JP6208615B2 - Transimpedance amplifier - Google Patents

Description

  The present invention relates to a transimpedance amplifier widely used in a receiver of an optical communication system, and more particularly to a method of constructing a transimpedance amplifier having high DC input tolerance.

  The receiver of the optical communication system converts the received optical signal into a voltage signal. As a configuration for realizing this function, a configuration is widely adopted in which a received optical signal is converted into a current signal by a photodiode, and the obtained current signal is converted into a voltage signal by a transimpedance amplifier. As a circuit configuration of the transimpedance amplifier, for example, a circuit configuration as shown in FIG. 14 described in Non-Patent Document 1 or a circuit configuration as shown in FIG. 15 described in Non-Patent Document 2 is known. Yes.

  The transimpedance amplifier having the circuit configuration of FIG. 14 is configured by a grounded emitter amplifier including a transistor Q1E and a resistor R1E. According to the transimpedance amplifier having the circuit configuration of FIG. 14, the current signal Iin input to the input terminal flows through the resistor RF1E. The transistor Q1E amplifies the voltage generated at the input terminal when the input current signal Iin flows through the resistor RF1E, and outputs the amplified voltage to the base of the transistor Q21E. The transistor Q21E functions as a buffer amplifier in combination with the current source I21E, and outputs the voltage signal Vout amplified by the grounded-emitter amplifier including the transistor Q1E and the resistor R1E to the output terminal.

  The transimpedance amplifier having the circuit configuration of FIG. 15 is configured by a grounded base amplifier including a transistor Q1 and a resistor R1. According to the transimpedance amplifier having the circuit configuration of FIG. 15, the current signal Iin input to the input terminal is input to the emitter of the transistor Q1, and most of it flows through the load resistor R1. Therefore, a voltage obtained by multiplying the input current signal Iin by R1 is output to the base of the transistor Q21. The transistor Q21 functions as a buffer amplifier in combination with the current source I21, and outputs the voltage signal Vout amplified by the grounded base amplifier including the transistor Q1 and the resistor R1 to the output terminal. The base voltage of the transistor Q1 is fixed to a constant voltage value VBB. The value of the direct current flowing through the transistor Q1 is fixed to a certain value by the current source I1 so that a necessary voltage gain value and band can be obtained.

  Also, depending on the optical communication system, transmission / reception may be performed using an optical phase modulation signal. In this case, the received optical signal is converted into two complementary light intensity modulation signals by an optical demodulator inside the receiver, and then the light intensity modulation signal is complementarily converted by a photodiode and a transimpedance amplifier. Is converted into a correct voltage signal. At this time, two transimpedance amplifiers as shown in FIG. 14 and FIG. 15 can be prepared in parallel, and the output of the transimpedance amplifiers can be amplified by a differential amplifier to obtain a differential voltage signal. Differential output voltage signals VoutP and VoutN can also be obtained using a differential transimpedance amplifier as shown in FIG. This circuit configuration is a differential version of the grounded emitter amplifier of FIG.

H. Fukuyama, et al., “InPhGaAs DHBT PARALLEL FEEDBACK AMPLIFIER WITH 14-dB GAJN AND 91-GHz BANDWIDTH”, 2004 International Conference on Indium Phosphide and Related Materials, pp.659-662, 2004 J. Martinez-Castillo, et al., “Transimpedance Amplifiers for Optical Fiber Systems Based on Common-Base Transistors”, Proceedings of the 1999 IEEE International Symposium on Circuits and Systems, Volume 6, pp. 85-88, 1999 H. Fukuyama, et al., “Two-channel InP HBT Differential Automatic gain-controlled Transimpedance Amplifier IC for 43-Gbit / s DQPSK photoreceiver”, Compound Semiconductor IC Symposium 2008, H.2, pp.145-148, Oct.2008

  Depending on the specifications of the communication system, a large dynamic range may be required for the input current amplitude. In the case of a transimpedance amplifier using a grounded-emitter amplifier, generally, the output is saturated when a signal having a large current amplitude is input because it is designed to have a large gain for high sensitivity. If the gain is reduced so that the output does not saturate, the sensitivity to a signal having a small current amplitude is deteriorated. Further, in order to absorb the direct current, it is necessary to provide a current drawing circuit at the input, noise characteristics are deteriorated, and sensitivity is further deteriorated.

  Also in the case of a transimpedance amplifier using a grounded base amplifier, when a current signal exceeding the bias current value by the current source I1 is input, the output is saturated. In order to prevent this output saturation, it is necessary to set the bias current value to be equal to or greater than the maximum current input value that can be input. In this case, power consumption increases. If the bias current value is set to be greater than or equal to the maximum input current value that can be input and the operation is continued under the condition that the input signal is small, useless power is consumed. Further, the voltage value of the output signal Vout of the common base amplifier varies depending on the DC value of the input signal Iin. As a result, the DC voltage at the input terminal of the next-stage amplifier connected to the transimpedance amplifier also fluctuates, making it impossible to operate the next-stage amplifier at an optimum bias point.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a transimpedance amplifier capable of obtaining a wide linear operation region without increasing power consumption.

  The transimpedance amplifier according to the present invention includes a transimpedance core circuit that amplifies an input current signal and simultaneously converts the current signal into a voltage signal and outputs the voltage signal to an output terminal of the transimpedance amplifier, and a voltage signal output to the output terminal of the transimpedance amplifier An average voltage detection circuit for detecting the average DC voltage of the voltage, an amplitude voltage detection circuit for detecting the amplitude voltage of the voltage signal output to the output terminal of the transimpedance amplifier, the average DC voltage detected by the average voltage detection circuit and the transformer A first feedback amplifier that amplifies a difference voltage from a DC voltage reference voltage indicating a desired DC potential at an output terminal of the impedance amplifier and applies negative feedback so as to adjust an amount of current flowing through the transistor of the transimpedance core circuit; Amplitude detected by the amplitude voltage detection circuit A second feedback amplifier that amplifies a voltage difference between the voltage and an amplitude voltage reference voltage indicating a desired signal amplitude at the output terminal of the transimpedance amplifier, and applies negative feedback to adjust the base voltage of the transistor of the transimpedance core circuit The transimpedance core circuit has a base terminal connected to the inverting output terminal of the second feedback amplifier, a collector terminal connected to the output terminal of the transimpedance amplifier, and an emitter terminal input to the transimpedance amplifier. A first transistor connected to the base, a base terminal connected to the non-inverting output terminal of the second feedback amplifier, a collector terminal connected to the positive power supply voltage, and an emitter terminal connected to the input terminal of the transimpedance amplifier Second transistor with one end at the positive power supply A load resistor having the other end connected to the collector terminal of the first transistor, a first terminal connected to the emitter terminals of the first and second transistors, and a second terminal being negative. And a variable current source connected to the non-inverting output terminal of the first feedback amplifier.

  The transimpedance amplifier of the present invention amplifies the input current signal and simultaneously converts it into a voltage signal and outputs it to the output terminal of the transimpedance amplifier, and outputs it to the output terminal of the transimpedance amplifier. An average voltage detection circuit that detects an average DC voltage of the voltage signal, an amplitude voltage detection circuit that detects an amplitude voltage of the voltage signal output to the output terminal of the transimpedance amplifier, and an average DC voltage detected by the average voltage detection circuit A first feedback amplifier that amplifies a difference voltage between the DC impedance and a DC voltage reference voltage indicating a desired DC potential at the output terminal of the transimpedance amplifier, and applies negative feedback so as to adjust the amount of current flowing through the transistor of the transimpedance core circuit The amplitude voltage detection circuit detects A second feedback that amplifies a difference voltage between the amplitude voltage and an amplitude voltage reference voltage indicating a desired signal amplitude at the output terminal of the transimpedance amplifier, and applies negative feedback to adjust the base voltage of the transistor of the transimpedance core circuit. The transimpedance core circuit has a base terminal connected to the inverting output terminal of the second feedback amplifier, a collector terminal connected to the output terminal of the transimpedance amplifier, and an emitter terminal input to the transimpedance amplifier. A first transistor connected to the terminal; a base terminal connected to the non-inverting output terminal of the second feedback amplifier; an emitter terminal connected to the input terminal of the transimpedance amplifier; Connected to the collector terminal of the second transistor A first load resistor whose other end is connected to the collector terminal of the first transistor, one end connected to the positive power supply voltage, and the other end connected to the collector terminal of the second transistor. 2 load resistors, a first terminal is connected to the emitter terminals of the first and second transistors, a second terminal is connected to the negative power supply voltage, and a current control terminal is connected to the first feedback amplifier. And a variable current source connected to the non-inverting output terminal.

  The transimpedance amplifier of the present invention includes a first transimpedance core circuit that amplifies the current signal input to the non-inverting input terminal and simultaneously converts the current signal to a voltage signal and outputs the voltage signal to the non-inverting output terminal of the transimpedance amplifier; A second transimpedance core circuit that amplifies the current signal input to the inverting input terminal and simultaneously converts it to a voltage signal and outputs it to the inverting output terminal of the transimpedance amplifier, and the non-inverting output terminal and the inverting output terminal of the transimpedance amplifier An average voltage detection circuit for detecting an average DC voltage of the voltage signal output to the non-inverting output terminal and the inverting output terminal of the transimpedance amplifier, an amplitude voltage detection circuit for detecting the amplitude voltage of the voltage signal, The average DC voltage detected by the average voltage detection circuit and the A first transimpedance core circuit and a second transimpedance core circuit that amplify a difference voltage between a differential non-inverting output terminal and a inverting output terminal of the impedance amplifier with a DC voltage reference voltage indicating a desired DC potential; A first feedback amplifier that applies negative feedback so as to adjust the amount of current flowing through the transistor, an amplitude voltage detected by the amplitude voltage detection circuit, and a desired signal amplitude at the non-inverting output terminal and the inverting output terminal of the transimpedance amplifier. A second feedback amplifier that amplifies a difference voltage from the amplitude voltage reference voltage shown and applies negative feedback so as to adjust base voltages of transistors of the first transimpedance core circuit and the second transimpedance core circuit; Comprising the first transimpedance core circuit and The second transimpedance core circuit has a base terminal connected to the inverting output terminal of the second feedback amplifier, a collector terminal connected to the output terminal of the transimpedance amplifier, and an emitter terminal connected to the input terminal of the transimpedance amplifier. The connected first transistor and the base terminal are connected to the non-inverting output terminal of the second feedback amplifier, the collector terminal is connected to the positive power supply voltage, and the emitter terminal is connected to the input terminal of the transimpedance amplifier. The second transistor, a load resistor having one end connected to the positive power supply voltage and the other end connected to the collector terminal of the first transistor, and a first terminal connected to the first and second transistors. The emitter terminal is connected, the second terminal is connected to the negative power supply voltage, and the current control terminal is the first feedback amplifier. And a variable current source connected to the non-inverting output terminal.

  The transimpedance amplifier of the present invention includes a first transimpedance core circuit that amplifies the current signal input to the non-inverting input terminal and simultaneously converts the current signal to a voltage signal and outputs the voltage signal to the non-inverting output terminal of the transimpedance amplifier; A second transimpedance core circuit that amplifies the current signal input to the inverting input terminal and simultaneously converts it to a voltage signal and outputs it to the inverting output terminal of the transimpedance amplifier, and the non-inverting output terminal and the inverting output terminal of the transimpedance amplifier An average voltage detection circuit for detecting an average DC voltage of the voltage signal output to the non-inverting output terminal and the inverting output terminal of the transimpedance amplifier, an amplitude voltage detection circuit for detecting the amplitude voltage of the voltage signal, The average DC voltage detected by the average voltage detection circuit and the A first transimpedance core circuit and a second transimpedance core circuit that amplify a difference voltage between a differential non-inverting output terminal and a inverting output terminal of the impedance amplifier with a DC voltage reference voltage indicating a desired DC potential; A first feedback amplifier that applies negative feedback so as to adjust the amount of current flowing through the transistor, an amplitude voltage detected by the amplitude voltage detection circuit, and a desired signal amplitude at the non-inverting output terminal and the inverting output terminal of the transimpedance amplifier. A second feedback amplifier that amplifies a difference voltage from the amplitude voltage reference voltage shown and applies negative feedback so as to adjust base voltages of transistors of the first transimpedance core circuit and the second transimpedance core circuit; Comprising the first transimpedance core circuit and The second transimpedance core circuit has a base terminal connected to the inverting output terminal of the second feedback amplifier, a collector terminal connected to the output terminal of the transimpedance amplifier, and an emitter terminal connected to the input terminal of the transimpedance amplifier. A first transistor connected, a base terminal connected to a non-inverting output terminal of the second feedback amplifier, an emitter terminal connected to an input terminal of the transimpedance amplifier, and one end of the second transistor 2 is connected to the collector terminal of the first transistor, the other end is connected to the collector terminal of the first transistor, one end is connected to the positive power supply voltage, and the other end is connected to the second transistor. A second load resistor connected to the collector terminal of the first and second terminals of the first and second transistors. A variable current source connected to the emitter terminal; a second terminal connected to the negative power supply voltage; and a current control terminal connected to the non-inverting output terminal of the first feedback amplifier. It is.

In addition, a configuration example of the transimpedance amplifier according to the present invention further includes a first buffer amplifier provided between a collector terminal of the first transistor and an output terminal of the transimpedance amplifier. Is.
In addition, a configuration example of the transimpedance amplifier of the present invention further includes a DC voltage reference voltage generation circuit that generates the DC voltage reference voltage, and the DC voltage reference voltage generation circuit has a base terminal that is the first transistor. A third transistor having a collector terminal connected to the output terminal of the DC voltage reference voltage generation circuit, one end connected to the positive power supply voltage, and the other end connected to the collector terminal of the third transistor. And a constant current source having a first terminal connected to the emitter terminal of the third transistor and a second terminal connected to the negative power supply voltage, and generating the DC voltage reference voltage The output terminal of the circuit is connected to the inverting input terminal of the first feedback amplifier.

In addition, a configuration example of the transimpedance amplifier of the present invention further includes a DC voltage reference voltage generation circuit that generates the DC voltage reference voltage, and the DC voltage reference voltage generation circuit has a base terminal that is the first transistor. A third transistor connected to the base terminal of the first transistor, a resistor having one end connected to the positive power supply voltage, the other end connected to the collector terminal of the third transistor, and a first terminal connected to the third transistor. A constant current source connected to the emitter terminal of the transistor and having the second terminal connected to the negative power supply voltage, and provided between the collector terminal of the third transistor and the output terminal of the DC voltage reference voltage generating circuit. And an output terminal of the DC voltage reference voltage generating circuit is connected to an inverting input terminal of the first feedback amplifier. A.
Also, one configuration example of the transimpedance amplifier according to the present invention is characterized in that the size of the second transistor of the transimpedance core circuit is larger than the size of the first transistor.
The transimpedance amplifier according to the present invention may further include an output terminal of the transimpedance core circuit and an input terminal of the average voltage detection circuit, an output terminal of the transimpedance amplifier, and an input of the amplitude voltage detection circuit. A linear amplifier provided between the terminal and the terminal is provided.
The transimpedance amplifier of the present invention further includes a control voltage buffer for controlling the gain of the linear amplifier so that the amplitude voltage detected by the amplitude voltage detection circuit matches the amplitude voltage reference voltage. It is characterized by comprising.
In one configuration example of the transimpedance amplifier of the present invention, the time constant of the first feedback amplifier is shorter than the time constant of the second feedback amplifier.

  According to the present invention, the transimpedance core circuit, the average voltage detection circuit, the amplitude voltage detection circuit, the first and second feedback amplifiers are provided, and the transimpedance core circuit is variable with the first and second transistors and the load resistance. By configuring with a current source, linearity can be maintained without distortion of the output amplitude of the transimpedance core circuit, and the DC voltage at the input terminal of the next stage amplifier connected to the transimpedance amplifier is set to an optimal constant value. Can keep. In addition, in the present invention, when the current signal input to the input terminal of the transimpedance amplifier is small, the amount of current drawn by the variable current source of the transimpedance core circuit is also controlled to a small value according to the current signal. The power consumption of the transimpedance amplifier can be reduced.

  Further, in the present invention, by dividing the load resistance of the first transistor of the transimpedance core circuit into two, the distortion characteristic at the minimum gain of the transimpedance core circuit can be improved.

  Further, in the present invention, the first buffer amplifier provided between the collector terminal of the first transistor and the output terminal of the transimpedance amplifier is provided, whereby the subsequent circuit connected to the output terminal of the transimpedance amplifier is provided. The driving force can be increased, and the influence from the subsequent circuit can be prevented from reaching the output of the transimpedance core circuit.

  In the present invention, the DC voltage reference voltage generation circuit is constituted by the third transistor, the resistor, and the constant current source, so that the DC voltage reference voltage output from the DC voltage reference voltage generation circuit can be converted into that of the transimpedance amplifier. A constant value can be maintained without depending on the input current value.

  In the present invention, the maximum input current amplitude allowed by the transimpedance amplifier can be increased by increasing the size of the second transistor of the transimpedance core circuit to be larger than the size of the first transistor. The dynamic range of the amplifier can be expanded.

  Further, in the present invention, by providing a linear amplifier between the output terminal of the transimpedance core circuit and the input terminal of the average voltage detection circuit and the output terminal of the transimpedance amplifier and the input terminal of the amplitude voltage detection circuit, the transimpedance The dynamic range of the amplifier can be expanded.

  In the present invention, the dynamic range of the transimpedance amplifier can be further expanded by using the linear amplifier as a variable gain amplifier.

  In the present invention, in the process in which the current component flowing through the load resistance of the first transistor is changed by making the time constant of the first feedback amplifier shorter than the time constant of the second feedback amplifier. The change in the direct current component flowing through the load resistance can be quickly compensated by the variable current source.

1 is a circuit diagram showing a configuration of a transimpedance amplifier according to a first embodiment of the present invention. It is a circuit diagram which shows the structure of the transimpedance amplifier which concerns on the 2nd Embodiment of this invention. It is a figure explaining the effect of the transimpedance amplifier which concerns on the 1st, 2nd embodiment of this invention. It is a circuit diagram which shows the structure of the transimpedance amplifier which concerns on the 3rd Embodiment of this invention. It is a circuit diagram which shows the structure of the transimpedance amplifier which concerns on the 4th Embodiment of this invention. It is a circuit diagram which shows the structure of the transimpedance amplifier which concerns on the 5th Embodiment of this invention. It is a circuit diagram which shows the structure of the transimpedance amplifier which concerns on the 6th Embodiment of this invention. It is a circuit diagram which shows the structure of the transimpedance amplifier which concerns on the 7th Embodiment of this invention. It is a circuit diagram which shows another structure of the transimpedance amplifier which concerns on the 7th Embodiment of this invention. It is a circuit diagram which shows the structure of the transimpedance amplifier which concerns on the 8th Embodiment of this invention. It is a circuit diagram which shows the structure of the transimpedance amplifier which concerns on the 9th Embodiment of this invention. It is a circuit diagram which shows the structure of the transimpedance amplifier which concerns on the 10th Embodiment of this invention. It is a circuit diagram which shows the structure of the transimpedance amplifier which concerns on the 11th Embodiment of this invention. It is a circuit diagram which shows the structure of the conventional transimpedance amplifier. It is a circuit diagram which shows another structure of the conventional transimpedance amplifier. It is a circuit diagram which shows another structure of the conventional transimpedance amplifier.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing a configuration of a transimpedance amplifier according to a first embodiment of the present invention. The transimpedance amplifier according to the present embodiment includes a transimpedance core circuit 1 that amplifies a current signal Iin input to an input terminal and simultaneously converts the current signal Iin to a voltage signal Vout, and a voltage signal Vout output to an output terminal of the transimpedance amplifier. An average voltage detection circuit 2 that detects the average DC voltage, an amplitude voltage detection circuit 3 that detects the amplitude voltage of the voltage signal Vout output to the output terminal of the transimpedance amplifier, and the average DC voltage detected by the average voltage detection circuit 2 And a feedback amplifier 4 that amplifies a difference voltage between a DC voltage reference voltage Vref1 indicating a desired DC potential at the output terminal of the transimpedance amplifier and applies negative feedback so as to adjust the amount of current flowing through the transistor of the transimpedance core circuit 1. Detected by the amplitude voltage detection circuit 3 A feedback amplifier 5 that amplifies a difference voltage between the width voltage and an amplitude voltage reference voltage Vref2 indicating a desired signal amplitude at the output terminal of the transimpedance amplifier and applies negative feedback to adjust the base voltage of the transistor of the transimpedance core circuit 1 It consists of.

  The transimpedance core circuit 1 includes a transistor Q1 having a base terminal connected to the inverting output terminal of the feedback amplifier 5, a collector terminal connected to the output terminal of the transimpedance amplifier, and an emitter terminal connected to the input terminal of the transimpedance amplifier. The transistor Q2 has a base terminal connected to the non-inverting output terminal of the feedback amplifier 5, a collector terminal connected to the positive power supply voltage VCC, an emitter terminal connected to the input terminal of the transimpedance amplifier, and one end connected to the positive power supply. The load resistor R1 is connected to the voltage VCC, the other end is connected to the collector terminal of the transistor Q1, the first terminal is connected to the emitter terminals of the transistors Q1 and Q2, and the second terminal is connected to the negative power supply voltage VEE. Connected, and the current control terminal is connected to the non-inverting output terminal of the feedback amplifier 4. Composed of the variable current source I1 Metropolitan was.

  In the transimpedance amplifier of the present embodiment, due to the circuit configuration of the transistors Q1 and Q2 of the transimpedance core circuit 1, the current signal Iin input to the input terminal is the control voltage input to the base terminals of the transistors Q1 and Q2. Depending on the difference voltage (the difference voltage between the non-inverted output voltage and the inverted output voltage of the feedback amplifier 5), the current flowing through the transistor Q1 and the current flowing through the transistor Q2 are separated. Among these, the current component converted into the voltage signal Vout by the load resistor R1 is only the current signal flowing through the transistor Q1.

  The amplitude voltage of the voltage signal Vout obtained by the load resistor R1 is detected by the amplitude voltage detection circuit 3. The feedback amplifier 5 amplifies a difference voltage between the amplitude voltage detected by the amplitude voltage detection circuit 3 and a predetermined amplitude voltage reference voltage Vref2, and applies negative feedback to the base terminals of the transistors Q1 and Q2. Thereby, the shunt ratio between the current flowing through the transistor Q1 and the current flowing through the transistor Q2 is adjusted so that the amplitude voltage detected by the amplitude voltage detection circuit 3 matches the amplitude voltage reference voltage Vref2. Thus, the amplitude of the voltage signal Vout can be maintained at a certain value so that the peak value of the voltage signal Vout is between the positive power supply voltage VCC and the average value of the voltage signal Vout.

  Further, the average voltage of the voltage signal Vout, that is, the DC voltage is detected by the average voltage detection circuit 2. The feedback amplifier 4 amplifies a difference voltage between the DC voltage detected by the average voltage detection circuit 2 and a predetermined DC voltage reference voltage Vref1, and applies negative feedback so as to adjust the current value of the variable current source 1. As a result, the DC current value flowing through the load resistor R1 is kept constant in consideration of the change in the shunt ratio between the current flowing through the transistor Q1 and the current flowing through the transistor Q2 in the transimpedance core circuit 1. As a result, the DC potential at the output terminal of the transimpedance amplifier is kept constant. That is, in the process of adjusting the control voltage input to the base terminals of the transistors Q1 and Q2, the current component flowing through the load resistor R1 among the DC component of the current signal Iin input to the input terminal of the transimpedance amplifier changes. The change is compensated by the variable current source I1, and the direct current component flowing through the load resistor R1 is kept at a constant value. In this way, control is performed so that the average DC voltage detected by the average voltage detection circuit 2 matches the DC voltage reference voltage Vref1. Conversely, when there is no negative feedback by the feedback amplifier 4 and the current value of the variable current source I1 is constant, the current flowing through the transistor Q1 and the transistor Q2 in the transimpedance core circuit 1 flow by the negative feedback by the feedback amplifier 5. Due to the change in the shunt ratio with the current, the DC potential at the output terminal of the transimpedance amplifier cannot be kept constant.

  As described above, according to the transimpedance amplifier of the present embodiment, linearity can be maintained without distortion of the output amplitude of the transimpedance core circuit 1, and the input terminal of the next-stage amplifier connected to the transimpedance amplifier. Can be maintained at an optimal constant value. In addition, when the current signal Iin input to the input terminal of the transimpedance amplifier is small, the amount of current drawn by the variable current source I1 is also controlled to a small value according to the current signal Iin. Electricity is also reduced.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. FIG. 2 is a circuit diagram showing a configuration of a transimpedance amplifier according to the second embodiment of the present invention. The same reference numerals are given to the same configurations as those in FIG. The transimpedance amplifier according to the present embodiment is the same as the transimpedance amplifier according to the first embodiment except that the output terminal of the transimpedance core circuit 1 (the connection point between the collector terminal of the transistor Q1 and the load resistor R1) and the transimpedance amplifier. The buffer amplifier 6 is provided between the output terminal of the first and second input terminals of the average voltage detection circuit 2 and the amplitude voltage detection circuit 3.

  In the present embodiment, the same effect as that of the first embodiment can be obtained, and the driving power for the subsequent circuit connected to the output terminal of the transimpedance amplifier can be increased by providing the buffer amplifier 6. In addition, it is possible to prevent the influence from the subsequent circuit from reaching the output of the transimpedance core circuit 1.

  FIG. 3 shows all harmonics of the voltage signal Vout output to the output terminal of the transimpedance amplifier when the circuit configuration of FIG. 2 is differentiated in order to confirm the effects of the first and second embodiments. FIG. 16 is a diagram comparing distortion and total harmonic distortion of a voltage signal Vout output to an output terminal of a transimpedance amplifier when the conventional circuit configuration illustrated in FIG. 15 is differentiated. 3 in FIG. 3 indicates the total harmonic distortion of the transimpedance amplifier obtained by differentiating the conventional circuit configuration of FIG. 15, and 31 indicates the total harmonic distortion of the transimpedance amplifier obtained by differentiating the circuit configuration of the present embodiment. Is shown.

  According to the circuit configuration of the conventional example, when the differential input current amplitude exceeds 0.5 mAppd, a total harmonic distortion of about 5% or more appears in the output waveform. For example, even if the differential input current amplitude exceeds 0.5 mAppd, the total harmonic distortion does not significantly deteriorate, and even if the differential input current amplitude exceeds 3 mAppd, the total harmonic distortion is 0. It is suppressed to about 2%.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. FIG. 4 is a circuit diagram showing a configuration of a transimpedance amplifier according to the third embodiment of the present invention. The same reference numerals are given to the same configurations as those in FIG. The transimpedance amplifier according to the present embodiment is the same as the transimpedance amplifier according to the first embodiment except that the output terminal of the transimpedance core circuit 1 (the connection point between the collector terminal of the transistor Q1 and the load resistor R1) and the average voltage detection circuit. The linear amplifier 7 is provided between the input terminal 2 and the output terminal of the transimpedance amplifier and the input terminal of the amplitude voltage detection circuit 3.

  In the present embodiment, the same effect as that of the first embodiment can be obtained, and the gain of the transimpedance core circuit 1 is lowered by providing the linear amplifier 7 as compared with the case where the linear amplifier 7 is not provided. Therefore, the dynamic range of the transimpedance amplifier can be expanded.

In this embodiment, one linear amplifier 7 is provided, but the output terminal of the transimpedance core circuit 1 and the input terminal of the average voltage detection circuit 2, the output terminal of the transimpedance amplifier, and the amplitude voltage detection circuit 3 A plurality of linear amplifiers 7 connected in cascade may be provided between these input terminals.
In this embodiment, an example in which the linear amplifier 7 is applied to the first embodiment is shown. However, the present invention is not limited to this, and the second and third embodiments and a later-described fourth embodiment. You may apply to embodiment.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described. FIG. 5 is a circuit diagram showing a configuration of a transimpedance amplifier according to a fourth embodiment of the present invention. The same reference numerals are given to the same configurations as those in FIG. The transimpedance amplifier according to the present embodiment is obtained by providing a transimpedance core circuit 1a instead of the transimpedance core circuit 1 in the transimpedance amplifier according to the first embodiment.

  The transimpedance core circuit 1a includes transistors Q1 and Q2, a variable current source I1, a load resistor R1A having one end connected to the collector terminal of the transistor Q2, and the other end connected to the collector terminal of the transistor Q1, and one end being positive. The load resistor R1B is connected to the side power supply voltage VCC and the other end is connected to the collector terminal of the transistor Q2. Thus, in this embodiment, the load resistance of the transistor Q1 is divided into two, R1A and R1B, and the collector terminal of the transistor Q2 is connected to the connection point of R1A and R1B.

  In the first embodiment, the single transimpedance gain of the transimpedance core circuit 1 can be changed in the range of 0 to R1. On the other hand, in the transimpedance core circuit 1a of the present embodiment, the single unit transimpedance gain can be changed only in the range of R1B to (R1A + R1B), and the minimum gain value is restricted. However, the distortion characteristic at the minimum gain of the transimpedance core circuit 1a of the present embodiment is better than the distortion characteristic at the same transimpedance gain of the transimpedance core circuit 1 of the first embodiment. There is an advantage of showing.

  In this embodiment, an example in which the transimpedance core circuit 1a is applied to the first embodiment is shown. However, the present invention is not limited to this, and is applied to the second and third embodiments. Also good.

  In the first to fourth embodiments, the output terminal of the amplitude voltage detection circuit 3 is connected to the non-inverting input terminal of the feedback amplifier 5, and the amplitude voltage reference voltage Vref 2 is input to the inverting input terminal of the feedback amplifier 5. However, such a connection method is an example, and is not limited to this, and is negative so that the amplitude voltage of the voltage signal Vout at the output terminal of the transimpedance amplifier matches the amplitude voltage reference voltage Vref2. Other connection methods may be used as long as feedback can be applied. For example, the peak voltage at the output terminal of the transimpedance amplifier and the average voltage at the output terminal are separately detected by the amplitude voltage detection circuit and are separately input to the feedback amplifier 5, and at the output terminal of the transimpedance amplifier inside the feedback amplifier 5. The amplitude voltage may be calculated. Another way of connection will be described in the following embodiment.

[Fifth Embodiment]
Next, a fifth embodiment of the present invention will be described. FIG. 6 is a circuit diagram showing a configuration of a transimpedance amplifier according to a fifth embodiment of the present invention. The same reference numerals are given to the same configurations as those in FIG. The present embodiment shows an example in which the circuit configuration of the first embodiment is embodied. The transimpedance amplifier according to the present embodiment includes a transimpedance core circuit 1, an average voltage detection circuit 2, an amplitude voltage detection circuit 3, feedback amplifiers 4 and 5, a DC voltage reference voltage generation circuit 8, and an amplitude voltage reference. And a voltage generation circuit 9.

  The configuration of the transimpedance core circuit 1 is as described in the first embodiment. In this embodiment, the base terminal (current control terminal of the variable current source I1) is the feedback amplifier 4 as the variable current source I1. Transistor Q10 having a collector terminal connected to the emitter terminals of transistors Q1 and Q2, one end connected to the emitter terminal of transistor Q10, and the other end connected to negative power supply voltage VEE. What consists of resistance R10 is used. Note that another known voltage-controlled current source may be used as the variable current source I1.

  The average voltage detection circuit 2 has one end (the input terminal of the average voltage detection circuit 2) connected to the output terminal of the transimpedance amplifier, one end connected to the other end of the resistor R31, and the other end connected to the negative power source. And a capacitor C30 connected to the voltage VEE. An output terminal of the average voltage detection circuit 2 (a connection point between the resistor R31 and the capacitor C30) is connected to a non-inverting input terminal of the feedback amplifier 4. Here, the average voltage detection circuit 2 is configured by an RC filter, but other known low-pass filter circuits may be used.

  The DC voltage reference voltage generation circuit 8 has a transistor Q51 whose base terminal is connected to the inverting output terminal of the feedback amplifier 5, one end connected to the positive power supply voltage VCC, and the other end connected to the collector terminal of the transistor Q51. The load resistor R51, and a constant current source I51 having a first terminal connected to the emitter terminal of the transistor Q51 and a second terminal connected to the negative power supply voltage VEE. The output terminal of the DC voltage reference voltage generation circuit 8 (the connection point between the collector terminal of the transistor Q51 and the load resistor R51) is connected to the inverting input terminal of the feedback amplifier 4.

  The DC voltage reference voltage Vref1 may be generated using a known constant voltage generation circuit. In the present embodiment, the DC voltage reference voltage generation circuit 8 includes a transistor Q51 having the same circuit constant as the transistor Q1. A base ground circuit comprising a load resistor R51 having the same circuit constant as the load resistor R1 and a constant current source I51 is used. This grounded base circuit is a replica circuit of the grounded base amplifier composed of the transistor Q1 and the load resistor R1. The current value of the constant current source I51 is matched with the current value of the variable current source I1 when the signal input to the input terminal of the transimpedance amplifier is in the no-input state, for example. If a replica circuit of a grounded base amplifier is used as the DC voltage reference voltage generation circuit 8, the voltage at the output terminal of the DC voltage reference voltage generation circuit 8, that is, the DC voltage reference voltage Vref1, does not depend on the input current value of the transimpedance amplifier. There is an advantage that a constant value can be maintained.

  The amplitude voltage detection circuit 3 includes a transistor Q41 whose base terminal (first input terminal of the amplitude voltage detection circuit 3) is connected to the output terminal of the transimpedance amplifier, and whose collector terminal is connected to the positive power supply voltage VCC. A transistor Q43 having a terminal connected to the emitter terminal of the transistor Q41, a collector terminal connected to the positive power supply voltage VCC, and a base terminal (second input terminal of the amplitude voltage detection circuit 3) is an output of the average voltage detection circuit 2. The transistor Q44 is connected to the terminal (the connection point between the resistor R31 and the capacitor C30), the collector terminal is connected to the positive power supply voltage VCC, the base terminal is connected to the emitter terminal of the transistor Q44, and the collector terminal is the positive power supply. The transistor Q45 connected to the voltage VCC and one end of the emitter of the transistor Q41 A capacitor C41 having the other end connected to the negative power supply voltage VEE, a first terminal connected to the emitter terminal of the transistor Q45, and a second terminal connected to the negative power supply voltage VEE. Source I42. The output terminal of the amplitude voltage detection circuit 3 (the connection point between the emitter terminal of the transistor Q45 and the constant current source I42) is connected to the inverting input terminal of the feedback amplifier 5.

  The amplitude voltage reference voltage generation circuit 9 has a resistor R41 having one end connected to the emitter terminal of the transistor Q43, a first terminal connected to the other end of the resistor R41, and a second terminal connected to the negative power supply voltage VEE. Constant current source I41. An output terminal of the amplitude voltage reference voltage generation circuit 9 (a connection point between the resistor R41 and the constant current source I41) is connected to a non-inverting input terminal of the feedback amplifier 5.

  Transistor Q41 and capacitor C41 form a peak detection circuit that detects the peak voltage of voltage signal Vout at the output terminal of the transimpedance amplifier. In the present embodiment, since the average voltage of the voltage signal Vout is also required in the amplitude voltage detection circuit 3, the output of the average voltage detection circuit 2 is used as the second input of the amplitude voltage detection circuit 3. Since the peak detection circuit comprising the transistor Q41 and the capacitor C41 is based on the principle of operation utilizing the base-emitter diode characteristics of the transistor Q41, the DC potential at the emitter terminal of the transistor Q41 is detected by the average voltage comprising the resistor R31 and the capacitor C30. The value is lower than the DC potential of the output terminal of the circuit 2 by the base-emitter voltage of the transistor Q41. For this reason, the transistor Q44 is added to the output of the average voltage detection circuit 2 to generate a voltage lower than the average voltage of the voltage signal Vout by the base-emitter voltage. The DC potential of the output of the voltage detection circuit 2 is aligned.

  The transistor Q43 and the constant current source I41 are buffers using an emitter follower. Similarly, the transistor Q45 and the constant current source I42 are buffers using an emitter follower. A resistor R41 is inserted between the emitter terminal of the transistor Q43 and the constant current source I41, and a voltage lower than the emitter terminal voltage of the transistor Q43 by (resistance value of R41 × current value of the constant current source I41) is fed back. The signal is input to the non-inverting input terminal of the amplifier 5. Therefore, the feedback amplifier 5 amplifies a voltage of (peak voltage of voltage signal Vout) − (average voltage of voltage signal Vout) − (resistance value of R41 × current value of constant current source I41).

Since the value obtained by subtracting the average voltage of the voltage signal Vout from the peak voltage of the voltage signal Vout is the amplitude of the voltage signal Vout, the value of (resistance value of R41 × current value of the constant current source I41) is a desired value of the voltage signal Vout. When the resistor R41 and the constant current source I41 are set so that the amplitude voltage reference voltage Vref2 indicating the amplitude is set, the feedback amplifier 5 amplifies the difference between the amplitude of the voltage signal Vout and the amplitude voltage reference voltage Vref2.
As the feedback amplifiers 4 and 5, a known differential amplifier may be used.

  Thus, in this embodiment, a specific circuit configuration of the transimpedance amplifier of the first embodiment can be realized, and the effects described in the first embodiment can be obtained.

[Sixth Embodiment]
Next, a sixth embodiment of the present invention will be described. FIG. 7 is a circuit diagram showing a configuration of a transimpedance amplifier according to the sixth embodiment of the present invention. The same reference numerals are given to the same configurations as those in FIGS. The present embodiment shows an example in which the circuit configuration of the second embodiment is embodied. The transimpedance amplifier according to the present embodiment includes a transimpedance core circuit 1, an average voltage detection circuit 2, an amplitude voltage detection circuit 3, feedback amplifiers 4 and 5, a buffer amplifier 6, and a DC voltage reference voltage generation circuit 8a. And an amplitude voltage reference voltage generation circuit 9.

  The buffer amplifier 6 has a base terminal (input terminal of the buffer amplifier 6) connected to an output terminal of the transimpedance core circuit 1 (a connection point between the collector terminal of the transistor Q1 and the load resistor R1), and a collector terminal connected to the positive power supply voltage. The transistor Q21 is connected to VCC, the emitter terminal (the output terminal of the buffer amplifier 6) is connected to the output terminal of the transimpedance amplifier, the first terminal is connected to the emitter terminal of the transistor Q21, and the second terminal is negative. And a constant current source I21 connected to the side power supply voltage VEE. Thus, in the present embodiment, an emitter follower circuit is used as the buffer amplifier 6.

  Thus, in the present embodiment, a specific circuit configuration of the transimpedance amplifier of the second embodiment can be realized, and the effects described in the second embodiment can be obtained.

  Note that the direct current potential at the output terminal of the transimpedance amplifier is lower than the base-emitter voltage of the transistor Q21 as compared with the first embodiment. Therefore, in the present embodiment, a buffer amplifier (emitter follower circuit) similar to the buffer amplifier 6 is provided in the DC voltage reference voltage generation circuit 8a. Specifically, this buffer amplifier has a base terminal connected to a connection point between the collector terminal of the transistor Q51 and the load resistor R51 (an output terminal of the DC voltage reference voltage generation circuit 8), and a collector terminal connected to the positive power supply voltage VCC. And a constant current source I52 having a first terminal connected to the emitter terminal of the transistor Q52 and a second terminal connected to the negative power supply voltage VEE. The output terminal of DC voltage reference voltage generation circuit 8a (the connection point between the emitter terminal of transistor Q52 and constant current source I52) is connected to the inverting input terminal of feedback amplifier 4.

[Seventh Embodiment]
In the configurations of the fifth and sixth embodiments, the base voltages of the transistors Q1 and Q2 of the transimpedance core circuit 1 are controlled by the differential output of the feedback amplifier 5, but the operation intended by the present invention is as follows. This can be obtained as long as negative feedback is applied to the voltage difference between the base voltages of the transistors Q1 and Q2. Therefore, as shown in FIG. 8, a constant control reference voltage Vref3 may be applied to the base terminals of the transistors Q1 and Q51. In this case, the feedback amplifier 5 generates a single-phase output voltage at the non-inverting output terminal so that a necessary difference voltage is generated with respect to the control reference voltage Vref3.

  Further, as shown in FIG. 9, a constant control reference voltage Vref3 may be applied to the base terminal of the transistor Q2. In the case of the configuration shown in FIG. 9, the feedback amplifier 5 generates a single-phase output voltage at the inverting output terminal so that a necessary difference voltage is generated with respect to the control reference voltage Vref3.

  The control reference voltage Vref3 is input from the feedback amplifier 5 to the base terminal of the transistor to which the control reference voltage Vref3 is not input, of the transistors Q1 and Q2, when the DC potential of the output terminal of the transimpedance amplifier is a desired value. It may be set to be equal to the direct current potential. As a circuit (not shown) for generating the control reference voltage Vref3, a known constant voltage generation circuit may be used.

  In this embodiment, the control reference voltage Vref3 is applied to the transistor Q1 or Q2 in the configuration of the sixth embodiment. However, in the configuration of the fifth embodiment shown in FIG. 6, the transistor Q1 or Q2 It goes without saying that the control reference voltage Vref3 may be applied to the power supply.

[Eighth Embodiment]
Next, an eighth embodiment of the present invention will be described. FIG. 10 is a circuit diagram showing a configuration of a transimpedance amplifier according to the eighth embodiment of the present invention. The same reference numerals are given to the same configurations as those in FIGS. This embodiment shows an example in which a circuit configuration obtained by applying the fourth embodiment to the second embodiment is embodied. The transimpedance amplifier of the present embodiment includes a transimpedance core circuit 1a, an average voltage detection circuit 2, an amplitude voltage detection circuit 3, feedback amplifiers 4 and 5, a buffer amplifier 6, and a DC voltage reference voltage generation circuit 8a. And an amplitude voltage reference voltage generation circuit 9.
The characteristics of the transimpedance core circuit 1a are as described in the fourth embodiment. Other circuit configurations are as described in the sixth embodiment.

[Ninth Embodiment]
Next, a ninth embodiment of the present invention will be described. FIG. 11 is a circuit diagram showing a configuration of a transimpedance amplifier according to the ninth embodiment of the present invention. The same reference numerals are given to the same configurations as those in FIGS. In the present embodiment, the circuit configuration of the sixth embodiment is changed so that differential current input is possible. The transimpedance amplifier of the present embodiment includes a transimpedance core circuit 1b, an average voltage detection circuit 2b, an amplitude voltage detection circuit 3b, feedback amplifiers 4 and 5, a buffer amplifier 6b, and a DC voltage reference voltage generation circuit 8a. And an amplitude voltage reference voltage generation circuit 9.

  The transimpedance core circuit 1b has a base terminal connected to the inverting output terminal of the feedback amplifier 5, an emitter terminal connected to the non-inverting input terminal of the transimpedance amplifier, and a base terminal connected to the non-inverting output of the feedback amplifier 5. A transistor Q2, a collector terminal connected to the positive power supply voltage VCC, an emitter terminal connected to the non-inverting input terminal of the transimpedance amplifier, and a base terminal connected to the inverting output terminal of the feedback amplifier 5. The transistor Q3 whose emitter terminal is connected to the inverting input terminal of the transimpedance amplifier, the base terminal is connected to the non-inverting output terminal of the feedback amplifier 5, the collector terminal is connected to the positive power supply voltage VCC, and the emitter terminal is transimpedance Connected to the inverting input terminal of the amplifier The transistor Q4, one end connected to the positive power supply voltage VCC, the other end connected to the collector terminal of the transistor Q1, the other end connected to the positive power supply voltage VCC, and the other end to the collector of the transistor Q3. The load resistor R2 connected to the terminal, the first terminal is connected to the emitter terminals of the transistors Q1 and Q2, the second terminal is connected to the negative power supply voltage VEE, and the current control terminal is the non-inversion of the feedback amplifier 4. The variable current source I1 connected to the output terminal, the first terminal is connected to the emitter terminals of the transistors Q3 and Q4, the second terminal is connected to the negative power supply voltage VEE, and the current control terminal is the feedback amplifier 4 And a variable current source I2 connected to a non-inverting output terminal. Differential input current signals IinP and IinN are input to the input terminals of the transimpedance amplifier.

As described in the fifth embodiment, the variable current source I1 includes the transistor Q10 and the resistor R10.
The variable current source I2 includes a transistor Q11 having a base terminal (current control terminal of the variable current source I2) connected to the non-inverting output terminal of the feedback amplifier 4 and a collector terminal connected to the emitter terminals of the transistors Q3 and Q4. Is connected to the emitter terminal of the transistor Q11 and the other end is connected to the negative power supply voltage VEE.

  The buffer amplifier 6b has a base terminal (a non-inverting input terminal of the buffer amplifier 6b) connected to a non-inverting output terminal (a connection point between the collector terminal of the transistor Q1 and the load resistor R1) of the transimpedance core circuit 1b. The transistor Q21 is connected to the positive power supply voltage VCC, the emitter terminal (the non-inverting output terminal of the buffer amplifier 6b) is connected to the non-inverting output terminal of the transimpedance amplifier, and the first terminal is connected to the emitter terminal of the transistor Q21. The constant current source I21 whose second terminal is connected to the negative power supply voltage VEE, and the base terminal (the inverting input terminal of the buffer amplifier 6b) are the inverting output terminal of the transimpedance core circuit 1b (the collector terminal of the transistor Q3) Connected to load resistor R2), collector terminal is positive The transistor Q22 is connected to the source voltage VCC, the emitter terminal (the inverting output terminal of the buffer amplifier 6b) is connected to the inverting output terminal of the transimpedance amplifier, the first terminal is connected to the emitter terminal of the transistor Q22, and the second Of the constant current source I22 connected to the negative power supply voltage VEE. Thus, the buffer amplifier 6b has an emitter follower circuit composed of the transistor Q21 and the constant current source I21, and an emitter follower circuit composed of the transistor Q22 and the constant current source I22.

The average voltage detection circuit 2b includes a resistor R31 having one end (first input terminal of the average voltage detection circuit 2b) connected to the non-inverting output terminal of the transimpedance amplifier and one end (second input of the average voltage detection circuit 2b). Terminal R) is connected to the inverting output terminal of the transimpedance amplifier, and a capacitor C30 having one end connected to the other end of the resistors R31 and R32 and the other end connected to the negative power supply voltage VEE. . An output terminal of the average voltage detection circuit 2b (a connection point between the resistors R31 and R32 and the capacitor C30) is connected to a non-inverting input terminal of the feedback amplifier 4.
The configuration of the DC voltage reference voltage generation circuit 8a is as described in the fifth and sixth embodiments.

  The amplitude voltage detection circuit 3b includes a transistor Q41 having a base terminal (first input terminal of the amplitude voltage detection circuit 3b) connected to the non-inverting output terminal of the transimpedance amplifier and a collector terminal connected to the positive power supply voltage VCC. , The base terminal (second input terminal of the amplitude voltage detection circuit 3b) is connected to the inverting output terminal of the transimpedance amplifier, the collector terminal is connected to the positive power supply voltage VCC, the base terminal is the transistor Q41, The transistor Q43 is connected to the emitter terminal of Q42, the collector terminal is connected to the positive power supply voltage VCC, and the base terminal (the third input terminal of the amplitude voltage detection circuit 3b) is the output terminal (resistance) of the average voltage detection circuit 2b. R31, R32 and capacitor C30), and the collector terminal is the positive power supply The transistor Q44 connected to the voltage VCC, the base terminal connected to the emitter terminal of the transistor Q44, the collector terminal connected to the positive power supply voltage VCC, and one end connected to the emitter terminals of the transistors Q41 and Q42. A capacitor C41 whose other end is connected to the negative power supply voltage VEE, a constant current source I42 whose first terminal is connected to the emitter terminal of the transistor Q45, and whose second terminal is connected to the negative power supply voltage VEE; Consists of The output terminal of the amplitude voltage detection circuit 3b (the connection point between the emitter terminal of the transistor Q45 and the constant current source I42) is connected to the inverting input terminal of the feedback amplifier 5. Of the amplitude voltage detection circuit 3b, the transistors Q41 and Q42 and the capacitor C41 constitute a peak detection circuit that detects the peak voltages of the differential output voltage signals VoutP and VoutN.

  The configuration of the amplitude voltage reference voltage generation circuit 9 is as described in the fifth embodiment. Thus, in this embodiment, a transimpedance amplifier in which the circuit configuration of the sixth embodiment is differentiated can be realized. In the present embodiment, the average voltage detection circuit 2b and the amplitude voltage detection circuit 3b simultaneously monitor complementary differential output voltage signals VoutP and VoutN, and perform the same control on the non-inverted input signal and the inverted input signal. Since the voltage is generated, there is an advantage that the symmetry between the amplification effect for the non-inverted input signal and the amplification effect for the inverted input signal can be kept good. In this embodiment, since the average voltage detection circuit 2b and the peak detection circuit in the amplitude voltage detection circuit 3b receive complementary differential output voltage signals VoutP and VoutN, the average voltage detection circuit 2b and the peak There is an advantage that the output voltage of the detection circuit converges quickly.

[Tenth embodiment]
Next, a tenth embodiment of the present invention will be described. FIG. 12 is a circuit diagram showing the configuration of the transimpedance amplifier according to the tenth embodiment of the present invention. Components similar to those in FIGS. 1, 6, 7, and 10 are given the same reference numerals. is there. In the present embodiment, the circuit configuration of the eighth embodiment is changed so that differential current input is possible. The transimpedance amplifier according to the present embodiment includes a transimpedance core circuit 1c, an average voltage detection circuit 2b, an amplitude voltage detection circuit 3b, feedback amplifiers 4 and 5, a buffer amplifier 6b, and a DC voltage reference voltage generation circuit 8a. And an amplitude voltage reference voltage generation circuit 9.

  The transimpedance core circuit 1c includes transistors Q1 to Q4, variable current sources I1 and I2, a load resistor R1A having one end connected to the collector terminal of the transistor Q2 and the other end connected to the collector terminal of the transistor Q1, and one end Is connected to the positive power supply voltage VCC, the other end is connected to the collector terminal of the transistor Q2, the one end is connected to the collector terminal of the transistor Q4, and the other end is connected to the collector terminal of the transistor Q3. The load resistor R2A is composed of a load resistor R2B having one end connected to the positive power supply voltage VCC and the other end connected to the collector terminal of the transistor Q4.

  Other configurations are the same as those described in the ninth embodiment. Thus, in this embodiment, a transimpedance amplifier in which the circuit configuration of the eighth embodiment is differentiated can be realized.

[Eleventh embodiment]
Next, an eleventh embodiment of the present invention will be described. FIG. 13 is a circuit diagram showing the configuration of the transimpedance amplifier according to the eleventh embodiment of the present invention. Components similar to those in FIGS. 1, 6, 7, 10, and 11 are designated by the same reference numerals. It is attached. In this embodiment, a linear amplifier 7 is provided between the output terminal of the buffer amplifier 6b and the output terminal of the transimpedance amplifier in the circuit configuration of the ninth embodiment. The transimpedance amplifier according to the present embodiment includes a transimpedance core circuit 1b, an average voltage detection circuit 2b, an amplitude voltage detection circuit 3c, feedback amplifiers 4 and 5, a buffer amplifier 6b, and a DC voltage reference voltage generation circuit 8a. And an amplitude voltage reference voltage generation circuit 9 and control voltage buffers 10 and 11.

  The transimpedance core circuit 1b, the average voltage detection circuit 2b, the feedback amplifiers 4 and 5, the buffer amplifier 6b, the DC voltage reference voltage generation circuit 8a, and the amplitude voltage reference voltage generation circuit 9 are as described in the ninth embodiment. is there.

  The non-inverting input terminal of the linear amplifier 7 is connected to the non-inverting output terminal (emitter terminal of the transistor Q21) of the buffer amplifier 6b, and the inverting input terminal is connected to the inverting output terminal (emitter terminal of the transistor Q22) of the buffer amplifier 6b. Yes. The non-inverting output terminal of the linear amplifier 7 is connected to the non-inverting output terminal of the transimpedance amplifier, and the inverting output terminal is connected to the inverting output terminal of the transimpedance amplifier.

  In the present embodiment, a variable gain linear amplifier is used as the linear amplifier 7, and the gain of the linear amplifier 7 is controlled by the control voltage output from the control voltage buffer 10. The non-inverting input terminal of the control voltage buffer 10 is connected to the non-inverting output terminal of the feedback amplifier 5, and the inverting input terminal is connected to the inverting output terminal of the feedback amplifier 5. When the amplitude voltage of the differential output voltage signals VoutP and VoutN becomes larger than the amplitude voltage reference voltage Vref2 determined by (resistance value of R41 × current value of the constant current source I41), the control voltage buffer 10 A control voltage is outputted so as to lower the gain, and when the amplitude voltage of the differential output voltage signals VoutP and VoutN becomes smaller than the amplitude voltage reference voltage Vref2, the control voltage is outputted so as to increase the gain of the linear amplifier 7. As a result, the amplitude voltages of the differential output voltage signals VoutP and VoutN are controlled to coincide with the amplitude voltage reference voltage Vref2. Thus, in combination with the adjustment of the shunt ratio between the current flowing through the transistor Q1 and the current flowing through the transistor Q2 and the adjustment of the shunt ratio between the current flowing through the transistor Q3 and the current flowing through the transistor Q4, the differential output voltage signal VoutP, The amplitude of VoutN can be kept constant.

  The non-inverting input terminal of the control voltage buffer 11 is connected to the non-inverting output terminal of the feedback amplifier 5, and the inverting input terminal is connected to the inverting output terminal of the feedback amplifier 5. The non-inverting output terminal of the control voltage buffer 11 is connected to the base terminals of the transistors Q2 and Q4, and the inverting output terminal is connected to the base terminals of the transistors Q1 and Q3.

  The amplitude voltage detection circuit 3c includes transistors Q41 to Q45, a capacitor C41, a constant current source I42, a resistor R42 having one end connected to the non-inverting output terminal of the buffer amplifier 6b (emitter terminal of the transistor Q21), and one end A resistor R43 connected to the inverting output terminal of the buffer amplifier 6b (emitter terminal of the transistor Q22), a capacitor C42 having one end connected to the other ends of the resistors R42 and R43, and the other end connected to the negative power supply voltage VEE Consists of

  In the present embodiment, the average voltage detection circuit 2b detects the average voltage at the output of the buffer amplifier 6b, whereas the amplitude voltage detection circuit 3c detects the amplitude voltage at the output of the transimpedance amplifier. The detection result of the average voltage detection circuit 2b cannot be used by the amplitude voltage detection circuit 3c. Therefore, an average voltage detection circuit comprising resistors R42 and R43 and a capacitor C42 is newly provided in the amplitude voltage detection circuit 3c. The output terminal of the average voltage detection circuit (the connection point between the resistors R42 and R43 and the capacitor C42) is connected to the base terminal of the transistor Q44.

  The linear amplifier 7 can be provided not only in this embodiment but also in other embodiments. The linear amplifier 7 may have a fixed gain or a variable gain as in the present embodiment. In particular, when the gain of the linear amplifier is variable, the dynamic range of the input current amplitude at the input terminal of the transimpedance amplifier can be absorbed by the two amplifiers of the transimpedance core circuit and the linear amplifier. There is an advantage that the dynamic range of the amplifier can be further expanded.

  In the first to eleventh embodiments, the size of the transistor Q2 is not necessarily the same as the size of the transistor Q1. Rather, when the size of the transistor Q2 is set larger than that of the transistor Q1, there is an advantage that a larger dynamic range can be obtained. That is, when the size of the transistor Q2 is N times the size of the transistor Q1, the maximum DC current value allowable by the transistor Q2 is also N times the maximum current value allowable by the transistor Q1. Therefore, when the maximum input current amplitude allowed by the transimpedance amplifier is compared between the case where the size of the transistor Q2 is N times the size of the transistor Q1 and the case where the size of the transistor Q2 is equal to the size of the transistor Q1, the transistor When the size of Q2 is N times the size of the transistor Q1, an input current amplitude that is approximately (N + 1) / 2 times larger than when the size of the transistor Q2 is equal to the size of the transistor Q1 can be tolerated. . Similarly, when the size of the transistor Q4 is set larger than that of the transistor Q3, there is an advantage that a larger dynamic range can be obtained. As a method of changing the size of the transistor, it can be realized by using transistors having literally different emitter sizes, but the effective transistor size can also be changed by connecting the transistors in parallel.

  In the first to eleventh embodiments, the time constant of the feedback amplifier 4 needs to be set shorter than the time constant of the feedback amplifier 5. This is because the control voltage input to the base terminals of the transistors Q1 to Q4 is adjusted by receiving the output of the amplitude voltage detection circuits 3, 3b, 3c, and the current signal input to the input terminal of the transimpedance amplifier This is because, in the process in which the current components flowing through the resistors R1 and R3 are changed, the change in the DC current components flowing through the resistors R1 and R3 is quickly compensated by the variable current sources I1 and I2.

  The present invention can be applied to a transimpedance amplifier.

  DESCRIPTION OF SYMBOLS 1,1a, 1b, 1c ... Transimpedance core circuit, 2, 2b ... Average voltage detection circuit, 3, 3b, 3c ... Amplitude voltage detection circuit, 4, 5 ... Feedback amplifier, 6, 6b ... Buffer amplifier, 7 ... Linear Amplifier, 8, 8a ... DC voltage reference voltage generation circuit, 9 ... Amplitude voltage reference voltage generation circuit, 10, 11 ... Control voltage buffer, Q1-Q4, Q10, Q11, Q21, Q22, Q41, Q42, Q43-Q45, Q51, Q52 ... transistors, R1, R1A, R1B, R2, R2A, R2B, R10, R11, R31, R32, R41, R42, R43, R51 ... resistors, C30, C41, C42 ... capacitors, I1, I2 ... variable current Source, I21, I22, I41, I42, I51, I52 ... constant current source.

Claims (11)

A transimpedance core circuit that amplifies the input current signal and simultaneously converts it into a voltage signal and outputs it to the output terminal of the transimpedance amplifier;
An average voltage detection circuit for detecting the average DC voltage of the voltage signal output to the output terminal of the transimpedance amplifier;
An amplitude voltage detection circuit for detecting the amplitude voltage of the voltage signal output to the output terminal of the transimpedance amplifier;
Amplifies the difference voltage between the average DC voltage detected by the average voltage detection circuit and the DC voltage reference voltage indicating the desired DC potential at the output terminal of the transimpedance amplifier, and adjusts the amount of current flowing through the transistor of the transimpedance core circuit A first feedback amplifier that applies negative feedback to
Amplifying a difference voltage between an amplitude voltage detected by the amplitude voltage detection circuit and an amplitude voltage reference voltage indicating a desired signal amplitude at an output terminal of the transimpedance amplifier, and adjusting a base voltage of a transistor of the transimpedance core circuit A second feedback amplifier for applying negative feedback,
The transimpedance core circuit has a base terminal connected to the inverting output terminal of the second feedback amplifier, a collector terminal connected to the output terminal of the transimpedance amplifier, and an emitter terminal connected to the input terminal of the transimpedance amplifier. A first transistor;
A second transistor having a base terminal connected to the non-inverting output terminal of the second feedback amplifier, a collector terminal connected to the positive power supply voltage, and an emitter terminal connected to the input terminal of the transimpedance amplifier;
A load resistor having one end connected to the positive power supply voltage and the other end connected to the collector terminal of the first transistor;
The first terminal is connected to the emitter terminals of the first and second transistors, the second terminal is connected to the negative power supply voltage, and the current control terminal is connected to the non-inverting output terminal of the first feedback amplifier. A transimpedance amplifier, characterized by comprising a variable current source. A transimpedance core circuit that amplifies the input current signal and simultaneously converts it into a voltage signal and outputs it to the output terminal of the transimpedance amplifier;
An average voltage detection circuit for detecting the average DC voltage of the voltage signal output to the output terminal of the transimpedance amplifier;
An amplitude voltage detection circuit for detecting the amplitude voltage of the voltage signal output to the output terminal of the transimpedance amplifier;
Amplifies the difference voltage between the average DC voltage detected by the average voltage detection circuit and the DC voltage reference voltage indicating the desired DC potential at the output terminal of the transimpedance amplifier, and adjusts the amount of current flowing through the transistor of the transimpedance core circuit A first feedback amplifier that applies negative feedback to
Amplifying a difference voltage between an amplitude voltage detected by the amplitude voltage detection circuit and an amplitude voltage reference voltage indicating a desired signal amplitude at an output terminal of the transimpedance amplifier, and adjusting a base voltage of a transistor of the transimpedance core circuit A second feedback amplifier for applying negative feedback,
The transimpedance core circuit has a base terminal connected to the inverting output terminal of the second feedback amplifier, a collector terminal connected to the output terminal of the transimpedance amplifier, and an emitter terminal connected to the input terminal of the transimpedance amplifier. A first transistor;
A second transistor having a base terminal connected to the non-inverting output terminal of the second feedback amplifier and an emitter terminal connected to the input terminal of the transimpedance amplifier;
A first load resistor having one end connected to the collector terminal of the second transistor and the other end connected to the collector terminal of the first transistor;
A second load resistor having one end connected to the positive power supply voltage and the other end connected to the collector terminal of the second transistor;
The first terminal is connected to the emitter terminals of the first and second transistors, the second terminal is connected to the negative power supply voltage, and the current control terminal is connected to the non-inverting output terminal of the first feedback amplifier. A transimpedance amplifier, characterized by comprising a variable current source. A first transimpedance core circuit that amplifies the current signal input to the non-inverting input terminal and simultaneously converts the current signal to a voltage signal and outputs the voltage signal to the non-inverting output terminal of the transimpedance amplifier;
A second transimpedance core circuit that amplifies the current signal input to the inverting input terminal and simultaneously converts it to a voltage signal and outputs it to the inverting output terminal of the transimpedance amplifier;
An average voltage detection circuit for detecting an average DC voltage of the voltage signal output to the non-inverting output terminal and the inverting output terminal of the transimpedance amplifier;
An amplitude voltage detection circuit for detecting the amplitude voltage of the voltage signal output to the non-inverting output terminal and the inverting output terminal of the transimpedance amplifier;
Amplifying a difference voltage between the average DC voltage detected by the average voltage detection circuit and a DC voltage reference voltage indicating a desired DC potential at the differential non-inverting output terminal and the inverting output terminal of the transimpedance amplifier, and the first transformer A first feedback amplifier that applies negative feedback to adjust the amount of current flowing through the transistors of the impedance core circuit and the second transimpedance core circuit;
Amplifying a difference voltage between the amplitude voltage detected by the amplitude voltage detection circuit and an amplitude voltage reference voltage indicating a desired signal amplitude at a non-inverted output terminal and an inverted output terminal of the transimpedance amplifier, and the first transimpedance core circuit And a second feedback amplifier that applies negative feedback to adjust a base voltage of a transistor of the second transimpedance core circuit,
The first transimpedance core circuit and the second transimpedance core circuit have a base terminal connected to the inverting output terminal of the second feedback amplifier, a collector terminal connected to the output terminal of the transimpedance amplifier, and an emitter A first transistor having a terminal connected to the input terminal of the transimpedance amplifier;
A second transistor having a base terminal connected to the non-inverting output terminal of the second feedback amplifier, a collector terminal connected to the positive power supply voltage, and an emitter terminal connected to the input terminal of the transimpedance amplifier;
A load resistor having one end connected to the positive power supply voltage and the other end connected to the collector terminal of the first transistor;
The first terminal is connected to the emitter terminals of the first and second transistors, the second terminal is connected to the negative power supply voltage, and the current control terminal is connected to the non-inverting output terminal of the first feedback amplifier. A transimpedance amplifier, characterized by comprising a variable current source. A first transimpedance core circuit that amplifies the current signal input to the non-inverting input terminal and simultaneously converts the current signal to a voltage signal and outputs the voltage signal to the non-inverting output terminal of the transimpedance amplifier;
A second transimpedance core circuit that amplifies the current signal input to the inverting input terminal and simultaneously converts it to a voltage signal and outputs it to the inverting output terminal of the transimpedance amplifier;
An average voltage detection circuit for detecting an average DC voltage of the voltage signal output to the non-inverting output terminal and the inverting output terminal of the transimpedance amplifier;
An amplitude voltage detection circuit for detecting the amplitude voltage of the voltage signal output to the non-inverting output terminal and the inverting output terminal of the transimpedance amplifier;
Amplifying a difference voltage between the average DC voltage detected by the average voltage detection circuit and a DC voltage reference voltage indicating a desired DC potential at the differential non-inverting output terminal and the inverting output terminal of the transimpedance amplifier, and the first transformer A first feedback amplifier that applies negative feedback to adjust the amount of current flowing through the transistors of the impedance core circuit and the second transimpedance core circuit;
Amplifying a difference voltage between the amplitude voltage detected by the amplitude voltage detection circuit and an amplitude voltage reference voltage indicating a desired signal amplitude at a non-inverted output terminal and an inverted output terminal of the transimpedance amplifier, and the first transimpedance core circuit And a second feedback amplifier that applies negative feedback to adjust a base voltage of a transistor of the second transimpedance core circuit,
The first transimpedance core circuit and the second transimpedance core circuit have a base terminal connected to the inverting output terminal of the second feedback amplifier, a collector terminal connected to the output terminal of the transimpedance amplifier, and an emitter A first transistor having a terminal connected to the input terminal of the transimpedance amplifier;
A second transistor having a base terminal connected to the non-inverting output terminal of the second feedback amplifier and an emitter terminal connected to the input terminal of the transimpedance amplifier;
A first load resistor having one end connected to the collector terminal of the second transistor and the other end connected to the collector terminal of the first transistor;
A second load resistor having one end connected to the positive power supply voltage and the other end connected to the collector terminal of the second transistor;
The first terminal is connected to the emitter terminals of the first and second transistors, the second terminal is connected to the negative power supply voltage, and the current control terminal is connected to the non-inverting output terminal of the first feedback amplifier. A transimpedance amplifier, characterized by comprising a variable current source. The transimpedance amplifier according to any one of claims 1 to 4,
The transimpedance amplifier further comprises a first buffer amplifier provided between the collector terminal of the first transistor and the output terminal of the transimpedance amplifier. The transimpedance amplifier according to any one of claims 1 to 4,
Furthermore, a DC voltage reference voltage generating circuit for generating the DC voltage reference voltage is provided,
The DC voltage reference voltage generating circuit is:
A third transistor having a base terminal connected to the base terminal of the first transistor and a collector terminal connected to the output terminal of the DC voltage reference voltage generation circuit;
A resistor having one end connected to the positive power supply voltage and the other end connected to the collector terminal of the third transistor;
A constant current source having a first terminal connected to the emitter terminal of the third transistor and a second terminal connected to a negative power supply voltage;
An output terminal of the DC voltage reference voltage generation circuit is connected to an inverting input terminal of the first feedback amplifier. The transimpedance amplifier according to claim 5.
Furthermore, a DC voltage reference voltage generating circuit for generating the DC voltage reference voltage is provided,
The DC voltage reference voltage generating circuit is:
A third transistor having a base terminal connected to the base terminal of the first transistor;
A resistor having one end connected to the positive power supply voltage and the other end connected to the collector terminal of the third transistor;
A constant current source having a first terminal connected to the emitter terminal of the third transistor and a second terminal connected to a negative power supply voltage;
A second buffer amplifier provided between the collector terminal of the third transistor and the output terminal of the DC voltage reference voltage generation circuit;
An output terminal of the DC voltage reference voltage generation circuit is connected to an inverting input terminal of the first feedback amplifier. The transimpedance amplifier according to any one of claims 1 to 7,
The transimpedance amplifier, wherein a size of the second transistor of the transimpedance core circuit is larger than a size of the first transistor. The transimpedance amplifier according to any one of claims 1 to 8,
And a linear amplifier provided between the output terminal of the transimpedance core circuit and the input terminal of the average voltage detection circuit, and the output terminal of the transimpedance amplifier and the input terminal of the amplitude voltage detection circuit. A characteristic transimpedance amplifier. The transimpedance amplifier of claim 9.
The linear amplifier is a variable gain amplifier;
The transimpedance amplifier further includes a control voltage buffer that controls the gain of the linear amplifier so that the amplitude voltage detected by the amplitude voltage detection circuit matches the amplitude voltage reference voltage. The transimpedance amplifier according to any one of claims 1 to 10,
The transimpedance amplifier, wherein a time constant of the first feedback amplifier is shorter than a time constant of the second feedback amplifier.

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