JP2008306615A - Gain adjustment control voltage supplying circuit and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gain adjustment control voltage supplying circuit capable of preventing the gain of a variable gain amplifier circuit from being varied even when external variation such as a temperature change or power supply voltage variation or noise is caused. <P>SOLUTION: On the basis of a result monitoring amplitudes of differential output voltage signals output from the positive-phase output voltage terminal VOT and the opposite-phase output voltage terminal VOC of a variable gain amplifier circuit, two voltage signals of a gain adjusting signal VGC for adjusting the gain of the gain variable amplifier circuit and the backward-phase reference potential REF of the gain adjusting signal are generated as a gain adjustment control voltage by an automatic gain control circuit 20 which outputs output signals of two phases, and supplied to base terminals of first and second gain adjustment transistors T3, T4 which constitute a gain adjustment circuit for adjusting the gain of the gain variable amplifier circuit. The gain variable amplifier circuit 20 includes an amplifier AMP, resistance R21, R22 for negative feedback and conductance C21, C22. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a gain adjustment control voltage supply circuit and a gain adjustment control voltage supply method, and more particularly, to a gain (amplification factor) of a variable gain amplifier (VGA) that performs differential amplification in a semiconductor integrated circuit. The present invention relates to a gain adjustment control voltage supply circuit that supplies a gain adjustment control voltage to a gain adjustment circuit (GCA: Gain Control Amplifier) that variably adjusts the gain and a method for supplying the gain adjustment control voltage.

  As an amplifier that amplifies a differential voltage signal with a variable gain, a block configuration shown in FIG. 6 is known in order to variably control the gain of a variable gain amplifier (VGA). In the amplifier of FIG. 6, a single variable gain amplifier circuit (VGA) 10 is shown, but a configuration in which a plurality of variable gain amplifier circuits (VGA) 10 are connected in multiple stages is also possible. In FIG. 6, when the differential input voltage signal Vin is input to the variable gain amplifier circuit (VGA) 10, the amplified differential output voltage signal Vout output from the variable gain amplifier circuit (VGA) 10 is monitored. In order to do this, it is input to an automatic gain controller (AGC) 20B. The automatic gain control circuit (AGC) 20B generates a gain control signal VGC for the variable gain amplifier circuit (VGA) 10 and outputs it to the variable gain amplifier circuit (VGA) 10.

  The variable gain amplifier circuit (VGA) 10 is a variable gain amplifier circuit that generates a current corresponding to the difference between the gain control signal VGC from the automatic gain control circuit (AGC) 20B and the reference potential REF from the reference potential generation circuit (RGC) 30B. By controlling so as to be supplied to (VGA) 10, a differential output voltage signal Vout having a target voltage level is output.

  In general, as shown in FIG. 6, the variable gain amplifier circuit (VGA) 10 includes a differential pair 11 for variably amplifying an input differential input voltage signal, and gain adjustment for adjusting the gain of the differential pair 11. The circuit 12 includes a constant current source 13 that supplies a constant current to the differential pair 11, and includes a gain control signal VGC from an automatic gain control circuit (AGC) 20B and a reference potential REF from a reference potential generation circuit (RGC) 30B. Is supplied to the gain adjustment circuit 12, adjusts the gain of the differential pair 11, and outputs a differential output voltage signal Vout having a target voltage level.

  Next, a specific circuit configuration of the variable gain amplifier circuit (VGA) 10 will be described with reference to FIG. FIG. 7 is a circuit diagram showing an example of the circuit configuration of the variable gain amplifier circuit. The circuit configuration of the variable gain amplifier circuit (VGA) 10 shown in FIG. 7 is an example of the circuit configuration previously filed by the present applicants, but “High” by Mamoru Ohara et al. “Gain Equalizing Amplifier Integrated Circuits for a Gigabit Optical Repeater”, IEEE Journal of Solid-State Circuits, vol. SC-20, No. 3, pp. 703-707 (1985) also describes a similar circuit configuration.

  The circuit configuration of the variable gain amplifier circuit (VGA) 10 shown in FIG. 7 is the same as the block configuration shown in FIG. 6, the differential pair 11 that amplifies the differential input voltage signal, and the gain adjustment that adjusts the gain of the differential pair 11. A circuit (GCA) 12 and a constant current source 13 for supplying a constant current to the differential pair 11 are provided. In FIG. 7, circuit elements (components) beginning with “T” are bipolar transistors, and circuit elements (components) starting with “R” are resistors. The terminal VCC is a collector-side power supply voltage terminal, the terminal VEE is an emitter-side power supply voltage terminal, the terminal VIT / VIC is a differential input voltage terminal to the differential pair 11 (the input voltage signal to the differential amplifier circuit is a differential voltage). And VOT / VOC are differential output voltage terminals (differential output terminals that output an output voltage signal from the differential amplifier circuit as a differential voltage).

  As shown in FIG. 7, the differential pair 11 includes a first amplifying transistor T1, a first collector resistance (load resistance) R1, a first first emitter resistance R3, and a first second emitter resistance R5. A second amplifier including a first amplifying circuit 11a, a second amplifying transistor T2, a second collector resistor (load resistor) R2, a second first emitter resistor R4, and a second second emitter resistor R6. The circuit 11b is composed of two amplifier circuits, and two sets of differential pairs are formed by two sets of emitter resistors, both of which are formed as a differential amplifier circuit that performs a differential amplification operation.

  One end of each of the first and second collector resistors R1 and R2 is connected to the collector of each of the first and second amplification transistors T1 and T2, and the emitter of the first amplification transistor T1 is connected to the emitter of the first and second amplification transistors T1 and T2. One end of the first emitter resistor R3 and the first second emitter resistor R5 are connected in parallel, and the second amplifying transistor T2 has an emitter connected to the second first emitter resistor R4 and the second two emitters. One end of the resistor R6 is connected in parallel. The other ends of the first and second collector resistors R1 and R2 are connected to the collector-side power supply voltage terminal VCC.

  Further, the gain adjustment circuit 12 performs two sets of differential amplification operations (that is, a differential operation based on a combination of two sets of emitter resistors R3, R5 and R4, R6). For the differential pair 11 configured to include 11b, each collector is connected to each of two different amplifier circuits 11a and 11b of the differential pair 11, and the emitters are commonly connected to provide a constant current source. 13 includes a first gain adjusting transistor T3 and a second gain adjusting transistor T4.

  That is, the gain adjustment circuit 12 includes the first gain adjustment transistor T3 that inputs the gain adjustment signal VGC from the automatic gain control circuit (AGC) 20B to the base terminal, and the reference potential from the reference potential generation circuit (RGC) 30B. It consists of a differential pair with a second gain adjusting transistor T4 that inputs REF to the base terminal. The emitters of the first and second gain adjusting transistors T3 and T4 are connected in common and connected to the constant current source 13. The collector of the first gain adjusting transistor T3 is connected to the first of the differential pair 11. The other ends of the first and second emitter resistors R3 and R4 are connected in parallel, and the collector of the second gain adjusting transistor T4 is connected to the first two and second two emitters of the differential pair 11. The other ends of the resistors R5 and R6 are connected in parallel. The constant current source 13 is connected to the emitter side power supply voltage terminal VEE.

  Here, the gain adjustment signal VGC of the automatic gain control circuit (AGC) 20B and the reference potential REF of the reference potential generation circuit (RGC) 30B applied to the bases of the first and second gain adjustment transistors T3 and T4, respectively. The two differential pairs (that is, two sets of emitter resistors) built in each of the first amplifier circuit 11a and the second amplifier circuit 11b of the differential pair 11 are switched according to the difference value of Or the current from the constant current source 13 flows separately in both directions, the differential pair 11 operates with different gains (amplification factors) and is applied to the differential input voltage terminals VIT / VIC of the differential pair 11. The input differential input voltage signal is amplified with a different gain (amplification factor) and output as a differential output voltage signal from the differential output voltage terminal VOT / VOC.

  For example, when the first gain adjustment transistor T3 is in the on state and the second gain adjustment transistor T4 is in the off state, only the first and second emitter resistors R3 and R4 have the constant current source 13 From the first and second emitter resistors R5 and R6, the gain of the variable gain amplifier circuit (VGA) 10 is the first and second collector resistors R1 and R6. The gain of the differential pair 11 is determined by the resistance value of R2, the resistance values of the first and second first emitter resistors R3 and R4, and the transconductance gm of the first and second amplifying transistors T1 and T2. The differential input voltage signal input to the differential input voltage terminal VIT / VIC is amplified by the gain and output from the differential output voltage terminal VOT / VOC as a differential output voltage signal.

  Conversely, when the first gain adjustment transistor T3 is in the off state and the second gain adjustment transistor T4 is in the on state, only the first and second emitter resistors R5 and R6 have a constant current source. 13 flows, and does not flow through the first and second emitter resistors R3 and R4. Therefore, the gain of the variable gain amplifier circuit (VGA) 10 is the first and second collector resistors R1. The gain of the differential pair 11 is determined by the resistance value of R2, the resistance values of the first and second emitter resistors R5 and R6, and the transconductance gm of the first and second amplifying transistors T1 and T2. The differential input voltage signal input to the differential input voltage terminal VIT / VIC is amplified by the gain and output from the differential output voltage terminal VOT / VOC as a differential output voltage signal.

  As described above, the on / off switching of the first and second gain adjustment transistors T3 and T4 is performed by changing the gain adjustment signal VGC of the automatic gain control circuit (AGC) 20B applied to each base. It is determined by the value of the difference from the reference potential REF of the reference potential generating circuit (RGC) 30B. When the difference between the two is sufficiently large, any of the first and second gain adjusting transistors T3 and T4 is selected. Only one of them is turned on and the other is turned off. As described above, the resistance value of the first first and second emitter resistors R3 and R4, or the first second and second two The gain G of the differential pair 11 is determined by switching to one of the resistance values of the emitter resistors R5 and R6.

  However, the gain adjustment signal VGC of the automatic gain control circuit (AGC) 20B applied to the respective bases of the first and second gain adjustment transistors T3 and T4 and the reference potential REF of the reference potential generation circuit (RGC) 30B When the difference value is not sufficiently large, the current from the constant current source 13 flows separately to the first and second gain adjusting transistors T3 and T4 at a ratio corresponding to the difference value between the two. Here, since the currents flowing through the first and second gain adjusting transistors T3 and T4 are currents from the constant current source 13, the sum of both currents is always constant.

  As described above, when the difference value between the two is not sufficiently large, the gain of the variable gain amplifier circuit (VGA) 10 is such that the first gain adjustment transistor T3 is completely on and the second gain adjustment. The intermediate between the gain when the transistor T4 is completely off and the gain when the first gain adjusting transistor T3 is completely off and the second gain adjusting transistor T4 is completely on Take a typical value.

  From the above, the gain adjustment signal VGC of the automatic gain control circuit (AGC) 20B applied to the bases of the first and second gain adjustment transistors T3 and T4 and the reference potential REF of the reference potential generation circuit (RGC) 30B By adjusting the difference value, the gain of the variable gain amplifier circuit (VGA) 10 of FIG. 7 can be continuously changed.

  That is, the differential input voltage signal which becomes the input signal for amplification is supplied to the bases of the first and second amplification transistors T1 and T2 forming the differential pair 13 (that is, the differential amplifier circuit). When applied via VIT / VIC, the magnitude of the voltage applied to the base of the first gain adjustment transistor T3 as the gain adjustment signal VGC for adjusting the gain of the differential pair 13 and the magnitude of the reference potential REF Depending on the value of the difference, the gain of the differential pair 13 (that is, the differential amplifier circuit) is changed over a wide range, and the collectors of the first and second amplification transistors T1 and T2, that is, the differential output voltage terminals VOT / VOC. Can be output as a differential output voltage signal after amplification.

  Next, in order to control the operation of the gain adjustment circuit 12 that adjusts the gain of the differential pair 11, the gain adjustment signal VGC and the reference potential REF are applied to the bases of the first and second gain adjustment transistors T3 and T4, respectively. The internal configuration of the automatic gain control circuit (AGC) 20B and reference potential generation circuit (RGC) 30B to be applied will be described with reference to FIG. FIG. 8 is a circuit diagram showing a circuit configuration example of an automatic gain control circuit that supplies a control voltage to a conventional gain adjustment circuit and a reference potential generation circuit. FIG. 8A shows a conventional automatic gain control circuit ( FIG. 8B shows a circuit configuration example of a conventional reference potential generation circuit (RGC) 30B.

  As shown in FIG. 8A, the automatic gain control circuit (AGC) 20B includes an amplifier AMP, negative feedback resistors R21 and R22, and conductances C21 and C22. The differential shown in FIG. A differential output voltage signal from the differential output voltage terminal VOT / VOC of the pair 11 is input, and a gain adjustment signal VGC corresponding to the amplitude of the differential output voltage signal is used as a gain adjustment signal of the differential pair 11. And output to the base terminal of the first gain adjusting transistor T3 of the gain adjusting circuit 12 shown in FIG.

On the other hand, as shown in FIG. 8B, the reference potential generation circuit (RGC) 30B is composed of transistors T31, T32, T33, T34 and resistors R31, R32, R33, and the variable gain amplification shown in FIG. A required voltage obtained by dividing the potential difference between the collector-side power supply voltage terminal VCC and the emitter-side power supply voltage terminal VEE shown in the circuit (VGA) by resistors R31 and R32 is applied to the base terminal of the transistor T33. As a result, the reference potential REF is output from the emitter of the transistor T33 to the base terminal of the second gain adjusting transistor T4 of the gain adjusting circuit 12 shown in FIG. Note that a terminal VCS in FIG. 8B is a constant current source voltage terminal, and the transistors T32 and T34 are set to the on state as long as the variable gain amplifier circuit (VGA) is operating.
Mamoru Ohara et al., “High Gain Equalizing Amplifier Integrated Circuits for a Gigabit Optical Repeater”, IEEE Journal of Solid-State Circuits, vol. SC-20, No. 3, pp. 703-707 (1985)

  In the conventional configuration, as shown in FIGS. 7 and 8, automatic gain control for outputting a single-phase gain control signal VGC in order to differentially operate the gain adjustment circuit 12 of the variable gain amplifier circuit (VGA) 10. The reference potential generation circuit (RGC) 30B is provided separately from the circuit (AGC) 20B, and the reference generated by the gain control signal VGC from the automatic gain control circuit (AGC) 20B and the reference potential generation circuit (RGC) 30B. The potential REF is supplied to the base terminals of the first and second gain adjusting transistors T3 and T4 constituting the differential pair of the gain adjusting circuit 12, respectively.

  As described above, the reference potential generation circuit (RGC) 30B that outputs the reference potential REF as a differential operation signal (voltage signal) of the gain adjustment circuit 12 is separate from the automatic gain control circuit (AGC) 20B. 8B, even if a circuit configuration relatively similar to the configuration of the automatic gain control circuit (AGC) 20B is used as shown in FIG. 8B, the reference potential generation circuit (RGC) ) The reference potential REF generated at 30B is in the same fluctuation state as the fluctuation of the gain control signal VGC from the automatic gain control circuit (AGC) 20B with respect to external fluctuations and noise such as temperature change and power supply voltage fluctuation. Cannot be set.

  As a result, as shown in FIG. 9, the gain of the variable gain amplifier circuit (VGA) 10 fluctuates greatly according to a temperature change, for example. FIG. 9 is a graph of a simulation result showing the influence of temperature change when the conventional method of supplying the control voltage to the gain adjustment circuit is used. The automatic gain control circuit (AGC) 20B having the circuit configuration of FIG. When the control voltage to the gain adjusting circuit 12, that is, the gain control signal VGC and the reference potential REF, is output by the reference potential generation circuit (RGC) 30B, the gain is variable at temperatures of 25 ° C. (solid line) and 90 ° C. (broken line). It shows how the gain of the amplifier circuit (VGA) 10 fluctuates.

  That is, at both 25 ° C. and 90 ° C., as shown in FIG. 9, a large gain fluctuation of about 2.5 dBV occurs over a wide range of the frequency band to be used.

  The present invention has been made in view of such problems, and the problem to be solved by the present invention is when external fluctuations such as temperature changes and power supply voltage fluctuations occur or when noise occurs. Another object of the present invention is to provide a gain adjustment control voltage supply circuit and a gain adjustment control voltage supply method capable of preventing fluctuations in gain of a variable gain amplifier circuit (VGA).

  The present invention comprises the following technical means in order to solve the above-mentioned problems.

  A first technical means is a gain adjustment control voltage supply circuit that generates and supplies a gain adjustment control voltage for adjusting a gain to a variable gain amplification circuit that performs differential amplification with variable gain. A single automatic gain control circuit that outputs a two-phase output signal is provided, and the gain of the variable gain amplifier circuit is determined based on the result of monitoring the amplitude of the differential output voltage signal output from the variable gain amplifier circuit. Two voltage signals of a gain adjustment signal to be adjusted and a reference potential having a phase opposite to that of the gain adjustment signal are generated and supplied by the single automatic gain control circuit as the gain adjustment control voltage. And

  A second technical means is a gain adjustment control voltage supply circuit that generates and supplies a gain adjustment control voltage for adjusting a gain to a variable gain amplifier circuit that performs differential amplification with variable gain. Two automatic gain control circuits having the same circuit configuration and the same circuit constant and outputting a single-phase output signal are provided, and the amplitude of the differential output voltage signal output from the variable gain amplifier circuit is determined. Based on the monitored result, one of each of two voltage signals, ie, a gain adjustment signal for adjusting the gain of the variable gain amplifier circuit and a reference potential having a phase opposite to that of the gain adjustment signal, is used for the gain adjustment. The control voltage is generated and supplied by each of the two automatic gain control circuits.

  According to a third technical means, in the control voltage supply circuit for gain adjustment described in the first or second technical means, the automatic gain control circuit includes an amplifier, a negative feedback resistor and a conductance. It is characterized by that.

  According to a fourth technical means, in the gain adjustment control voltage supply circuit according to any one of the first to third technical means, the variable gain amplifier circuit amplifies a differential input voltage signal and outputs a differential output. A differential pair that outputs as a voltage signal, a gain adjustment circuit that adjusts the gain of the differential pair, and a constant current source that supplies a constant current to the differential pair are generated as the control voltage for gain adjustment. Two voltage signals of the gain adjustment signal and the reference potential are supplied to the gain adjustment circuit.

  According to a fifth technical means, in the control voltage supply circuit for gain adjustment according to the fourth technical means, the differential pair includes two sets of two amplifier circuits that perform differential amplification operation. In the gain adjustment circuit, the collectors of the first gain adjustment transistor and the second gain adjustment transistor, the emitters of which are commonly connected and connected to the constant current source, are different from each other of the differential pair. Each of the two amplifier circuits in the set is connected to each other, supplies the gain adjustment signal to the base terminal of the first gain adjustment transistor, and supplies the reference potential to the base of the second gain adjustment transistor. It supplies to a terminal, It is characterized by the above-mentioned.

  According to a sixth technical means, in the gain adjustment control voltage supply method, the gain adjustment control voltage for adjusting the gain is generated and supplied to the variable gain amplifier circuit that performs differential amplification with variable gain. A single control circuit that outputs a two-phase output signal is provided, and the gain of the variable gain amplifier circuit is adjusted based on the result of monitoring the amplitude of the differential output voltage signal output from the variable gain amplifier circuit. Two voltage signals of a gain adjustment signal and a reference potential having a phase opposite to that of the gain adjustment signal are generated and supplied by the single control circuit as the gain adjustment control voltage.

  According to a seventh technical means, in the gain adjustment control voltage supply method, the gain adjustment control voltage for adjusting the gain is generated and supplied to the variable gain amplifier circuit that performs differential amplification with variable gain. Two control circuits having the same circuit configuration and the same circuit constant and outputting a single-phase output signal are provided, and the amplitude of the differential output voltage signal output from the variable gain amplifier circuit is monitored. Based on the result, one of two voltage signals each of a gain adjustment signal for adjusting the gain of the variable gain amplifier circuit and a reference potential having a phase opposite to that of the gain adjustment signal is applied to the gain adjustment control voltage. As described above, the control circuit is generated and supplied by each of the two control circuits.

  According to the gain adjustment control voltage supply circuit and the gain adjustment control voltage supply method of the present invention, the gain adjustment is performed with respect to the gain adjustment circuit that variably adjusts the gain (amplification factor) of the variable gain amplification circuit that performs differential amplification. A two-phase automatic gain control that outputs a gain adjustment signal supplied as a control voltage and a reference potential, a differential output voltage signal of a variable gain amplifier circuit, and outputs two output signals of normal phase and reverse phase Since it is configured to be supplied from a circuit or from two single-phase automatic gain control circuits having the same circuit type and the same circuit constant, the following effects can be obtained.

  According to external fluctuations such as temperature changes and power supply voltage fluctuations and noise levels, both the gain adjustment signal and the reference potential can be output as values with similar level fluctuations. The monitoring result of the amplitude of the differential output voltage signal of the moving pair can be accurately reflected, and the gain for obtaining a desired differential output voltage signal can be adjusted. Thus, as in the prior art, it is possible to prevent the influence of external fluctuations such as temperature changes and power supply voltage fluctuations, and gain fluctuations caused by noise, which occur when the gain adjustment signal and the reference potential are generated using separate circuits. Can do.

  Further, by outputting a gain adjustment control voltage signal to be supplied to the gain adjustment circuit from a single circuit called a two-phase automatic gain control circuit, that is, a gain adjustment signal and a reference potential, the gain adjustment control voltage supply circuit It is possible to reduce the size and secure the degree of freedom in the layout of the variable gain amplifier.

  Hereinafter, an example of the best embodiment of the gain adjustment control voltage supply circuit and the gain adjustment control voltage supply method according to the present invention will be described in detail with respect to the gain adjustment control voltage supply circuit with reference to the drawings. .

(Example of overall configuration of the present invention)
The gain adjustment control voltage supply circuit according to the present invention is applied to an amplifier capable of amplifying a differential voltage signal with a variable gain. As shown in FIG. 1, the block configuration of the amplifier is different from the block configuration shown in FIG. 6 in the prior art, and includes an automatic gain control circuit (AGC) 20B and a reference potential generation circuit (RGC) 30B separately. Instead, an automatic gain control circuit (AGC) 20B that outputs a gain adjustment signal and a reference potential generation circuit (RGC) 30B that outputs a reference potential REF are integrated into a gain adjustment control voltage supply circuit (GCS: Gain). Control Voltage Supplier) 40. FIG. 1 is a block configuration diagram showing a block configuration of an amplifier to which a gain adjustment control voltage supply circuit according to the present invention is applied.

  That is, the gain adjustment control voltage supply circuit (GCS) 40 shown in FIG. 1 has a gain adjustment signal VGC for gain adjustment and a reference potential REF for a variable gain amplifier (VGA) constituting a variable gain amplifier. (Gain adjustment signal VGC and opposite phase signal) and the same circuit (automatic gain control circuit (AGC) for outputting two-phase output signals of normal phase and opposite phase, or the same circuit configuration and the same circuit) The circuit is configured to output from two automatic gain control circuits (AGCs) that consist of constants and output a single-phase output signal. In the amplifier shown in FIG. 1, a single variable gain amplifier circuit (VGA) 10 is shown, but a configuration in which a plurality of variable gain amplifier circuits (VGA) 10 are connected in multiple stages is also possible.

  In FIG. 1, when the differential input voltage signal Vin is input to the variable gain amplifier circuit (VGA) 10, the differential output voltage signal Vout output from the variable gain amplifier circuit (VGA) 10 is the same as that of FIG. Unlike the case of the amplifier, it is input to the gain adjustment control voltage supply circuit (GCS) 40. The gain adjustment control voltage supply circuit 40 generates a gain control signal VGC for the variable gain amplifier circuit (VGA) 10, outputs it to the variable gain amplifier circuit (VGA) 10, and compares it with the gain control signal VGC. A power reference potential REF is also generated and output to the variable gain amplifier circuit (VGA) 10 as in the case of the conventional amplifier of FIG.

  The variable gain amplifier circuit (VGA) 10 supplies a current corresponding to the difference between the gain control signal VGC from the gain adjustment control voltage supply circuit (GCS) 40 and the reference potential REF to the variable gain amplifier circuit (VGA) 10. By controlling the supply, a differential output voltage signal Vout having a target voltage level is output.

  In general, as shown in FIG. 1, the variable gain amplifier circuit (VGA) 10 includes a differential pair 11 and a differential pair 11 for variably amplifying an input differential input voltage signal, as in FIG. A gain adjustment circuit 12 for adjusting the gain of the signal, and a constant current source 13 for supplying a constant current to the differential pair 11, and a gain control signal VGC and a reference potential REF from a gain adjustment control voltage supply circuit (GCS) 40. Are supplied to the gain adjustment circuit 12, adjust the gain of the differential pair 11, and output a differential output voltage signal Vout having a target voltage level.

  Next, an example of a specific circuit configuration of the variable gain amplifier circuit (VGA) 10 to which the control voltage supply circuit for gain adjustment according to the present invention is applied will be described with reference to FIG. FIG. 2 is a circuit diagram showing an example of a circuit configuration of a variable gain amplifier circuit (VGA) 10 to which the gain adjustment control voltage supply circuit (GCS) according to the present invention is applied.

  The circuit configuration of the variable gain amplifier circuit (VGA) 10 shown in FIG. 2 is a circuit other than the circuit portion connecting the gain adjustment control voltage supply circuit (GCS) 40 according to the present invention to the gain adjustment circuit 12. 7 is exactly the same as the circuit configuration shown as the prior art in FIG. 7, and the gain control signal VGC supplied to the gain adjustment circuit 12 and the reference potential REF also operate as the variable gain amplifier circuit (VGA) 10. Is the same as that described in FIG. 7 except that it is supplied from the gain adjustment control voltage supply circuit (GCS) 40 instead of from the automatic gain control circuit 20B and the reference potential generation circuit 30B in FIG. Therefore, detailed description here is omitted.

(First embodiment)
Next, a configuration example of the gain adjustment control voltage supply circuit (GCS) 40 according to the present invention will be described with reference to FIG. FIG. 3 is a circuit diagram showing an example of the circuit configuration of the gain adjustment control voltage supply circuit according to the present invention. The circuit configuration has a single two-phase type automatic gain control circuit (AGC) 20 incorporated therein. An example is shown.

  The automatic gain control circuit (AGC) 20 incorporated in the gain adjustment control voltage supply circuit 40 includes an amplifier AMP, negative feedback resistors R21 and R22 (resistance values are the same), and conductances C21 and C22 (capacitance values are the same). Are connected to the differential output voltage terminals VOT / VOC of the variable gain amplifier circuit (VGA) 10 to be gain controlled, and the variable gain amplifier circuit ( VGA) Based on the result of monitoring the differential output voltage signal output from 10, the gain adjustment signal VGC corresponding to the amplitude level of the differential output voltage signal, the reference potential REF (the voltage opposite in phase to the gain adjustment signal VGC) Signal) is generated by the differential amplification operation and is output to the base terminals of the first and second gain adjusting transistors T3 and T4 of the gain adjusting circuit 12 shown in FIG.

  That is, in the gain adjustment control voltage supply circuit (GCS) 40 of FIG. 3, the gain adjustment circuit (GCA) 12 that variably adjusts the gain (amplification factor) of the variable gain amplification circuit (VGA) 10 that performs differential amplification. The gain adjustment signal VGC supplied as a gain adjustment control voltage and the reference potential REF are monitored, and the differential output voltage signal of the variable gain amplifier circuit (VGA) 10 is monitored, and two outputs of normal phase and negative phase are output. It is characterized in that it is output as a voltage signal for gain adjustment control consisting of two voltage signals of a normal phase and a reverse phase from the same circuit, which is a two-phase automatic gain control circuit (AGC) 20 that outputs a signal. have.

  As a result, even if external fluctuations such as temperature changes and power supply voltage fluctuations and noise occur, a single circuit such as a two-phase automatic gain control circuit (AGC) 20 can cause temperature changes and power supply voltage fluctuations. It is possible to output both the gain adjustment signal VGC and the reference potential REF from the positive phase output terminal and the negative phase output terminal as values with the same level fluctuation in accordance with external fluctuations and noise levels. The operation of the circuit (GCA) 12 can be performed by accurately reflecting the monitoring result of the amplitude of the differential output voltage signal of the differential pair 11 and adjusted to a gain for obtaining a desired differential output voltage signal. It becomes possible to do. Thus, as in the prior art, the effects of external variations such as temperature changes and power supply voltage fluctuations, and gain fluctuations caused by noise, which occur when the gain adjustment signal VGC and the reference potential REF are generated using separate circuits, are prevented. can do.

  Further, a gain adjustment control voltage signal, that is, a gain adjustment signal VGC and a reference potential REF supplied to the gain adjustment circuit (GCA) 12 from a single circuit of the two-phase automatic gain control circuit (AGC) 20 are output. Accordingly, the size of the gain adjustment control voltage supply circuit (GCS) 40 can be reduced, and the degree of freedom in the layout of the gain variable amplifier can be secured.

(Second embodiment)
Next, a circuit configuration example having a different configuration of the gain adjustment control voltage supply circuit (GCS) according to the present invention will be described with reference to FIG. FIG. 4 is a circuit diagram showing another example of the circuit configuration of the gain adjustment control voltage supply circuit according to the present invention, which is different from FIG. 3, and includes single-phase automatic gain control circuits (AGC) 20A ₁ and 20A ₂ . The example which consists of a circuit structure of the form which incorporated two pieces is shown.

The two single-phase automatic gain control circuits (AGC) 20A ₁ and 20A ₂ incorporated in the gain adjustment control voltage supply circuit (GCS) 40A shown in FIG. 4 use the same circuit configuration and the same circuit constants. Each of them has a circuit configuration having an amplifier AMP, negative feedback resistors R21 and R22, and conductances C21 and C22, and both circuit elements have the same circuit constant. The two input terminals of the positive phase and the negative phase are both connected to the differential output voltage terminal VOT / VOC of the variable gain amplifier circuit (VGA) 10 to be gain controlled. The method is such that the differential output voltage terminals VOT / VOC are crossed, and the output signals are both extracted from the output terminals on the same reverse phase side.

As described above, the _two automatic gain control circuits (AGC) 20A ₁ and 20A ₂ built in the gain adjustment control voltage supply circuit 40A in FIG. 4 are each a gain variable amplification circuit (VGA) to be gain controlled. 10 are connected to the differential output voltage terminals VOT / VOC, and as a result, as with the case of the gain adjustment control voltage supply circuit (GCS) 40 of FIG. Based on the result of monitoring the differential output voltage signal, the automatic gain control circuit (AGC) 20A ₁ side outputs the gain adjustment signal VGC corresponding to the amplitude level of the differential output voltage signal and the automatic gain control circuit (AGC). ) in 20A ₂ side, the reference potential REF corresponding to the amplitude level of the differential output voltage signal (voltage signal having a phase opposite to that of the gain adjustment signal VGC), respectively generated, the gain control circuit 12 shown in FIG. 2 Respectively output to the base terminal of the one-second gain adjusting transistor T3-T4.

That is, in the gain adjustment control voltage supply circuit (GCS) 40A of FIG. 4, as in the gain adjustment control voltage supply circuit (GCS) 40 of FIG. A gain adjustment signal VGC supplied as a gain adjustment control voltage and a reference potential REF to a gain adjustment circuit (GCA) 12 that variably adjusts a gain (amplification factor) and a reference potential REF have the same circuit configuration and circuit constants. It is characterized in that it is output from each single-phase variable gain amplifier (VGA) 20A ₁ , 20A ₂ as a voltage signal for gain adjustment control consisting of two voltage signals of normal phase and reverse phase. have.

As a result, even if external fluctuations such as temperature changes and power supply voltage fluctuations and noises occur, gains from two variable gain amplifiers (VGA) 20A ₁ and 20A _{2 having the} same circuit configuration and circuit constants are obtained. Since the adjustment signal VGC and the reference potential REF are generated, a value in which both the gain adjustment signal VGC and the reference potential REF fluctuate in substantially the same manner in accordance with external fluctuations such as temperature changes and power supply voltage fluctuations and noise levels. The gain adjustment circuit (GCA) 12 can be made to reflect the monitoring result of the amplitude of the differential output voltage signal of the differential pair 11 almost accurately. It is possible to adjust the gain for obtaining the differential output voltage signal. Thus, as in the prior art, the effects of external variations such as temperature changes and power supply voltage fluctuations, and gain fluctuations caused by noise, which occur when the gain adjustment signal VGC and the reference potential REF are generated using separate circuits, are prevented. can do.

In the circuit configuration shown in FIG. 4, for both automatic gain control circuits (AGC) 20A ₁ and 20A ₂ , two input terminals of normal phase and reverse phase are crossed to differential output voltage terminals VOT / VOC. In this case, both output signals are taken out from the same negative phase output terminal. However, in some cases, two input terminals of the positive phase and the negative phase are connected to the same differential output voltage terminal VOT / VOC. It is also possible to connect straightly as they are and to take out the output signals of both from the output terminals on the negative phase side and the positive phase side. Furthermore, in some cases, the two input terminals of the positive phase and the negative phase on the side of the automatic gain control circuit (AGC) 20A ₂ that outputs the reference potential REF are not connected to the differential output voltage terminals VOT / VOC. Alternatively, an open state may be used.

As described in the first and second embodiments above, in the gain adjustment control voltage supply circuits (GCS) 40 and 40A showing one configuration example according to the present invention, the variable gain amplifier circuit for performing differential amplification A gain adjustment signal VGC supplied as a gain adjustment control voltage and a reference potential REF to a gain adjustment circuit (GCA) 12 that variably adjusts the gain (amplification factor) of the (VGA) 10 and a reference potential REF are two-phase automatic gain control circuits. (AGC) 20 or two single-phase automatic gain control circuits (AGC) 20A ₁ and 20A _{2 having the} same circuit configuration / circuit constant are generated as differential output voltages. A circuit configuration having resistance to external fluctuations such as voltage fluctuations and noise can be realized, and gain fluctuations of the variable gain amplifier circuit (VGA) 10 can be suppressed.

  For example, when the temperature changes between 25 ° C. and 90 ° C., the gain of the variable gain amplifier circuit (VGA) 10 is only about 0.24 dBV over a wide range of frequency bands to be used, as shown in FIG. Can be suppressed. FIG. 5 is a graph of simulation results showing the effect of temperature change on the gain when the gain adjustment control voltage supply circuit (GCS) of the present invention is used, and the gain adjustment control voltage supply having the circuit configuration of FIG. In the case where the control voltage, that is, the gain control signal VGC and the reference potential REF are supplied to the gain adjustment circuit 12 by the circuit (GCS) 40, the variable gain amplification circuit when the temperature is 25 ° C. (solid line) and 90 ° C. (broken line) It shows how the gain of (VGA) fluctuates.

  In the above description, the gain adjustment control voltage supply circuit including the automatic gain control circuit (AGC) that monitors the amplitude of the differential output voltage signal of the variable gain amplifier circuit (VGA) 10 has been described. The present invention is not limited to such a case. The automatic gain control signal VGC is generated as a gain adjustment control voltage supply circuit separately from the automatic gain control circuit (AGC) that monitors the amplitude of the differential output voltage signal. A gain control circuit (AGC) may be added separately.

  Furthermore, the voltage levels of the two control voltages supplied for gain adjustment to the differential pair constituting the gain adjustment circuit 12 of the variable gain amplifier circuit (VGA) are external fluctuations such as power supply voltage fluctuations and temperature changes. As long as the supply method is such that the amount of fluctuation does not differ depending on the noise and the amount of fluctuation, the control circuit having any circuit configuration can be adopted, and the gain adjustment of the present invention As a control voltage supply method, the control circuit may be different from the circuit configuration described above.

  In each of the embodiments described above, among the amplifier (AMP), the negative feedback resistor, and the conductance constituting the automatic gain control circuit (AGC), the conductance is not only realized by using a capacitor, but also in the case Depending on the case, a capacitance component due to wiring may be used.

1 is a block configuration diagram showing a block configuration of an amplifier to which a gain adjustment control voltage supply circuit according to the present invention is applied. 1 is a circuit diagram showing an example of a circuit configuration of a variable gain amplifier circuit to which a gain adjustment control voltage supply circuit according to the present invention is applied. FIG. It is a circuit diagram which shows an example of the circuit structure of the control voltage supply circuit for gain adjustment which concerns on this invention. It is a circuit diagram which shows the other example of the circuit structure of the control voltage supply circuit for gain adjustment which concerns on this invention. It is a graph of the simulation result which shows the influence of the temperature change with respect to the gain of the variable gain amplifier circuit to which the control voltage supply circuit for gain adjustment which concerns on this invention is applied. It is a block block diagram which shows the block structure of the amplifier which controls the gain of the conventional variable gain amplifier circuit variably. It is a circuit diagram which shows an example of the circuit structure of the conventional variable gain amplifier circuit. It is a circuit diagram which shows the circuit structural example of the automatic gain control circuit and reference potential generation circuit which are supplied as a control voltage to the conventional gain adjustment circuit. It is a graph of the simulation result which shows the influence of the temperature change with respect to the gain of a variable gain amplifier circuit at the time of using the supply method of the control voltage to the conventional gain adjustment circuit.

Explanation of symbols

10 ... variable gain amplifier (VGA), 11 ... differential pair, 12 ... gain adjustment circuit, 13 ... constant current _source, 20, 20A 1, _20A 2, 20B ... automatic gain control circuit (AGC), 30B ... reference potential Generation circuit (RGC), 40, 40A... Gain adjustment control voltage supply circuit (GCS).

Claims (7)

  In a gain adjustment control voltage supply circuit that generates and supplies a gain adjustment control voltage for adjusting the gain to a variable gain amplifier circuit that performs differential amplification with variable gain, outputs a two-phase output signal A gain adjustment signal for adjusting the gain of the variable gain amplifier circuit based on the result of monitoring the amplitude of the differential output voltage signal output from the variable gain amplifier circuit; Two voltage signals having a reference potential opposite in phase to the gain adjustment signal are generated and supplied by the single automatic gain control circuit as the gain adjustment control voltage. Supply circuit.   A gain adjustment control voltage supply circuit that generates and supplies a gain adjustment control voltage for adjusting a gain to a variable gain amplifier circuit that performs differential amplification with variable gain, and has the same circuit configuration, and , Having two automatic gain control circuits having the same circuit constant and outputting a single-phase output signal, based on the result of monitoring the amplitude of the differential output voltage signal output from the variable gain amplifier circuit, Any one of two voltage signals of a gain adjustment signal for adjusting the gain of the variable gain amplifier circuit and a reference potential having a phase opposite to that of the gain adjustment signal is used as the gain adjustment control voltage. A control voltage supply circuit for gain adjustment, which is generated and supplied by each of the automatic gain control circuits.   3. The gain adjustment control voltage supply circuit according to claim 1, wherein the automatic gain control circuit includes an amplifier, a negative feedback resistor, and a conductance. Supply circuit.   4. The gain adjustment control voltage supply circuit according to claim 1, wherein the variable gain amplifier circuit amplifies a differential input voltage signal and outputs the differential input voltage signal as a differential output voltage signal; A gain adjustment circuit for adjusting the gain of the differential pair, and a constant current source for supplying a constant current to the differential pair, and the gain adjustment signal generated as the gain adjustment control voltage and the reference potential A control voltage supply circuit for gain adjustment, wherein two voltage signals are supplied to the gain adjustment circuit.   5. The gain adjustment control voltage supply circuit according to claim 4, wherein the differential pair is configured to include two sets of two amplification circuits that perform differential amplification operation, and the gain adjustment circuit includes an emitter. The collectors of the first gain adjustment transistor and the second gain adjustment transistor, which are connected in common and connected to the constant current source, are respectively connected to the two amplifier circuits of the different pairs of the differential pair. The gain is characterized in that the gain adjustment signal is supplied to the base terminal of the first gain adjustment transistor, and the reference potential is supplied to the base terminal of the second gain adjustment transistor. Control voltage supply circuit for adjustment.   In a gain adjustment control voltage supply method for generating and supplying a gain adjustment control voltage for adjusting a gain to a variable gain amplifier circuit that performs differential amplification with variable gain, a two-phase output signal is output. A gain control signal for adjusting the gain of the variable gain amplifier circuit based on the result of monitoring the amplitude of the differential output voltage signal output from the variable gain amplifier circuit, and the gain A method for supplying a control voltage for gain adjustment, characterized in that two voltage signals having a reference potential opposite in phase to the adjustment signal are generated and supplied by the single control circuit as the control voltage for gain adjustment.   In a gain adjustment control voltage supply method for generating and supplying a gain adjustment control voltage for adjusting a gain to a variable gain amplifier circuit that performs differential amplification with variable gain, the same circuit configuration, and And two control circuits having the same circuit constant and outputting a single-phase output signal, and based on the result of monitoring the amplitude of the differential output voltage signal output from the variable gain amplifier circuit, the gain One of two voltage signals each of a gain adjustment signal for adjusting the gain of the variable amplifier circuit and a reference potential having a phase opposite to that of the gain adjustment signal is used as the gain adjustment control voltage. A method of supplying a control voltage for gain adjustment, characterized by being generated and supplied by each circuit.

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