CN107359865B - Transimpedance amplifier - Google Patents

Abstract

The present disclosure provides a transimpedance amplifier including a first stage transconductance amplifier, a second stage transconductance amplifier, a third stage amplifier, and a feedback circuit. The first-stage transconductance amplifier is electrically connected to the input current source to receive the first input signal and output a first output signal. The second-stage transduction amplifier is electrically connected to the first-stage transduction amplifier to receive the first output signal and output a second output signal. The third-stage amplifier is electrically connected to the second-stage transduction amplifier to receive the second output signal and output a third output signal. One end of the feedback circuit is electrically connected to the first-stage transduction amplifier, and the other end of the feedback circuit is electrically connected to the third-stage amplifier to stabilize the third output signal. The third stage amplifier is composed of a first output stage and a second output stage. The present disclosure can shorten the time of the transmission delay of the transimpedance amplifier.

Description

Transimpedance amplifier

technical field

The present invention relates to a trans-impedance amplifier (Trans-Conductance Amplifier; TIA), in particular to a trans-impedance amplifier that will shorten the transmission delay time.

Background technique

In the optical communication system, the gain and sensitivity of the optical receiver are very important characteristics, and both must be improved to optimize the transmission efficiency. The single-stage (Single-Stage) transimpedance amplifier used in traditional optical receivers has a simple structure, but since the overall gain and bandwidth characteristics are closely related to the output impedance of the amplifier, the structure of the single-stage transimpedance amplifier will be affected by The voltage gain is insufficient and there is a problem that high sensitivity cannot be obtained.

Therefore, a multi-stage (Multi-Stage) transimpedance amplifier structure is generally used to design an optical receiver to achieve high voltage gain. The architecture of this multi-stage transimpedance amplifier usually consists of multiple single amplifiers in series, but since the input current of the photoreceiver depends on the infrared light received by the photodiode, the maximum and minimum input current may differ by a factor of four . The difference between the maximum value and the minimum value of the input current will increase the propagation delay of the output terminal of the transimpedance amplifier from high to low.

SUMMARY OF THE INVENTION

The embodiment of the present invention discloses a transimpedance amplifier, which includes a first-stage transconductance amplifier, a second-stage transconductance amplifier, a third-stage amplifier and a feedback circuit. The first-stage transconductance amplifier has an input end and an output end. The input end of the first-stage transconductance amplifier is electrically connected to the input current source to receive the first input signal, and then the output end of the first-stage transconductance amplifier is connected to the input current source. A first output signal is output. The second-stage transconductance amplifier has an input end and an output end, and the input end of the second-stage transconductance amplifier is electrically connected to the output end of the first-stage transconductance amplifier to receive the first output signal, and then the second-stage transconductance amplifier The output terminal of the stage transconductance amplifier outputs a second output signal. The third-stage amplifier has an input end and an output end, and the input end of the third-stage amplifier is electrically connected to the output end of the second-stage transconductance amplifier to receive the second output signal, and then the output of the third-stage amplifier The terminal outputs a third output signal. One end of the feedback circuit is electrically connected to the input end of the first-stage transconductance amplifier, and the other end of the feedback circuit is electrically connected to the output end of the third-stage amplifier to stabilize the third output signal. The third-stage amplifier is composed of a first output stage and a second output stage.

In one embodiment of the present invention, the first output stage of the third-stage amplifier includes a current source, one end of which is electrically connected to the supply voltage source to provide a stable current, and the other end of which is connected to the output end of the third-stage amplifier.

In one embodiment of the present invention, the second output stage of the third stage amplifier includes a first NMOS transistor and a second PMOS transistor. The gate of the first NMOS transistor is connected to the gate of the second PMOS transistor to form the input of the third stage amplifier. The source of the second PMOS transistor is electrically connected to the supply voltage source, and the drain of the second PMOS transistor and the drain of the first NMOS transistor are connected to the output end of the third-stage amplifier. The drain of the first NMOS transistor is grounded.

In one of the embodiments of the present invention, the transimpedance amplifier includes a reference voltage circuit. The reference voltage circuit includes a constant current unit, a third transistor, a fourth transistor and a fifth transistor. The constant current unit includes a current mirror and a bias current source. The gate of the third transistor, the gate of the fourth transistor and the current mirror are connected in parallel with each other. The drain of the fourth transistor forms an output terminal of the reference voltage circuit to output a reference voltage signal. The fifth transistor is connected in parallel with the constant current unit, and is electrically connected between the supply voltage source and the output end of the constant current source.

To sum up, the transimpedance amplifier proposed in the embodiment of the present invention is provided with a third-stage amplifier composed of a first output stage and a second output stage, wherein the circuit design of the first output stage belongs to the group of class A amplifiers. The circuit design of the second output stage belongs to the configuration of the class AB amplifier. In this way, the transimpedance amplifier can have the advantages of both class A amplifier and class AB amplifier, and the transmission delay time of the transimpedance amplifier can be shortened. . On the other hand, in the reference voltage circuit of the transimpedance amplifier proposed in the embodiment of the present invention, the fifth transistor is arranged in parallel with the constant current unit, and is electrically connected between the supply voltage source and the output end of the reference voltage circuit, In order to improve the instability of the reference voltage signal caused by temperature changes or changes in the manufacturing process.

In order to further understand the features and technical content of the present invention, please refer to the following detailed description and accompanying drawings of the present invention, but these descriptions and drawings are only used to illustrate the present invention, rather than make any claim to the scope of the present invention. limits.

Description of drawings

FIG. 1 is a circuit diagram of a transimpedance amplifier disclosed in an embodiment of the present invention.

FIG. 2 is a circuit diagram of a transimpedance amplifier disclosed in another embodiment of the present invention.

FIG. 3 is a circuit diagram of a transimpedance amplifier disclosed in another embodiment of the present invention.

FIG. 4A is a graph showing the variation of a reference voltage signal with temperature in the transimpedance amplifier disclosed in the embodiment shown in FIG. 2 .

FIG. 4B is a graph showing the variation of the reference voltage signal with temperature in the transimpedance amplifier disclosed in the embodiment shown in FIG. 3 .

Detailed ways

Various embodiments will be described more fully hereinafter with reference to the accompanying drawings, in which some embodiments are shown. However, the inventive concepts may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are disclosed so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concept to those skilled in the art. Throughout the drawings, like numerals indicate similar components.

It will be understood that, although the terms first, second, third, etc. may be used herein to describe various components, these components should not be limited by these terms. These terms are used to distinguish one element from another. Accordingly, a first component discussed below could be referred to as a second component without departing from the teachings of the present inventive concept. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

[Example of Transimpedance Amplifier]

Please refer to FIG. 1 , which is a circuit diagram of a transimpedance amplifier disclosed in an embodiment of the present invention. As shown in FIG. 1 , the transimpedance amplifier 1 includes a first-stage transconductance amplifier TCA1 , a second-stage transconductance amplifier TCA2 , a third-stage amplifier TSA3 and a feedback circuit FB. The first-stage transconductance amplifier TCA1 has an input end and an output end, and the input end of the first-stage transconductance amplifier TCA1 is electrically connected to the input current source Iin to receive the first input signal, and then the first-stage transconductance amplifier TCA1 The output terminal of TCA1 outputs the first output signal. The second-stage transconductance amplifier TCA2 has an input end and an output end, and the input end of the second-stage transconductance amplifier TCA2 is electrically connected to the output end of the first-stage transconductance amplifier TCA1 to receive the first output signal, and then the The output terminal of the second-stage transconductance amplifier TCA2 outputs a second output signal. The third-stage amplifier TSA3 has an input terminal and an output terminal. The input terminal of the third-stage amplifier TSA3 is electrically connected to the output terminal of the second-stage transconductance amplifier TCA2 to receive the second output signal. The output terminal of the amplifier TSA3 outputs the third output signal TIAp. One end of the feedback circuit FB is electrically connected to the input end of the first-stage transconductance amplifier TCA1, and the other end of the feedback circuit FB is electrically connected to the output end of the third-stage amplifier TSA3 to stabilize the third output signal TIAp. The third-stage amplifier TSA3 includes a first output stage OUT1 and a second output stage OUT2.

What will be taught next is to further explain the working principle of the transimpedance amplifier 1 . As shown in FIG. 1 , the third-stage amplifier TSA3 of the transimpedance amplifier 1 of this embodiment is composed of a first output stage OUT1 and a second output stage OUT2. The first output stage OUT1 includes a current source Is, wherein one end of the current source Is is electrically connected to the supply voltage source Vcc to provide a stable current, and the other end of the current source Is is connected to the output end of the third stage amplifier TSA3. The second output stage OUT2 includes a first NMOS transistor MN1 and a second PMOS transistor MP2. The gate of the first NMOS transistor MN1 is connected with the gate of the second PMOS transistor MP2 to form the input terminal of the third stage amplifier TSA3. The source of the second PMOS transistor MP2 is electrically connected to the supply voltage source Vcc, and the drain of the second PMOS transistor MP2 and the drain of the first NMOS transistor MN1 are connected to the output terminal of the third-stage amplifier TSA3. The source of the first NMOS transistor MN1 is grounded. That is, the first output stage OUT1 belongs to the class A output stage, and the second output stage OUT2 belongs to the class AB output stage. In addition, in this embodiment, the third-stage amplifier TSA3 may further include a second NMOS transistor MN2. As shown in FIG. 1 , the gate and source of the second NMOS transistor MN2 are connected to the output terminal of the third-stage amplifier TSA3 .

In this embodiment, the first output stage OUT1 is a current source Is connected to a reference voltage source (not shown), and the stable current provided by the first output stage OUT1 is a constant value. When the aforementioned input current source Iin starts to input current, the current flowing through the first NMOS transistor MN1 increases, and at the same time, the current flowing through the second PMOS transistor MP2 decreases, so that the voltage value of the third output signal TIAp increases. Finally, the output voltage of the transimpedance amplifier 1 is controlled by the resistors R1 and R2 in the feedback circuit FB, and the base-emitter voltage of the bipolar junction transistor B1.

It is worth noting that, in this embodiment, since the third-stage amplifier TSA3 has both a class A output stage and a class AB output stage, it can have both the advantages of the class A output stage and the class AB output stage in circuit design. That is to say, the components of the first output stage OUT1 are maintained in an on state, and better linearity is disclosed, and at the same time, the second output stage OUT2 can further improve the efficiency of the third stage amplifier TSA3.

On the other hand, it should be noted in this embodiment that the first-stage transconductance amplifier TCA1 and the second-stage transconductance amplifier TCA2 are both class-A output stages, and the first-stage transconductance amplifier TCA1 and the second-stage transconductance amplifier TCA1 The amplifier TCA2 and the third-stage amplifier TSA3 are connected in series in a direct coupling manner. That is to say, there are no capacitors between the first-stage transconductance amplifier TCA1, the second-stage transconductance amplifier TCA2, and the third-stage amplifier TSA3. Therefore, when designing the circuit, the size ratio between the transistors must be specially designed. , so that the sensitivity of the overall transimpedance amplifier to temperature and different processes can be improved.

Besides, please refer to FIG. 1 again, the feedback circuit FB in this embodiment includes a bipolar junction transistor B1 and a resistor network RC. The emitter of the bipolar junction transistor B1 is electrically connected to the input current source Iin, and the base and the collector of the bipolar junction transistor B1 are connected to the output end of the third-stage amplifier TSA3. In addition, the resistor network RC is connected in parallel with the bipolar junction transistor B1, and includes a bridge T-shaped network composed of three resistors R1-R3 and a capacitor C1, wherein one end of the capacitor C1 is electrically connected to the bridge form a T-shaped network, and the other end of the capacitor C1 is grounded. Further, the feedback circuit FB can increase the gain of the transimpedance amplifier 1 of this embodiment, wherein the bipolar junction transistor B1 in the feedback circuit FB is used to clamp the third output signal TIAp to stabilize the third output signal TIAp.

[Another embodiment of a transimpedance amplifier]

In order to describe the circuit design of the transimpedance amplifier according to the present invention in more detail, another embodiment will be given below for further explanation.

In the following embodiments, parts different from those of the above-described embodiment of FIG. 1 will be described, and the remaining omitted parts are the same as those of the above-described embodiment of FIG. 1 . Also, for convenience of description, like reference numerals or numerals refer to like components.

Please refer to FIG. 2 , which is a circuit diagram of a transimpedance amplifier disclosed in another embodiment of the present invention. The difference from the embodiment shown in FIG. 1 is that in this embodiment, the transimpedance amplifier 2 further includes a reference voltage circuit, which is connected in parallel with the third-stage amplifier TSA3, and includes a constant current unit I′, a first Three transistors MP3, a fourth transistor MP4, a sixth transistor MN6 and a resistor R4. As shown in FIG. 2 , the constant current unit I′ includes a current mirror MR and a bias current source I _Bias . The third transistor MP3, the fourth transistor MP4 and the current mirror MR are connected in parallel with each other, and the drain of the fourth transistor MP4 forms the output terminal of the reference voltage circuit REF to output the reference voltage signal TIAn. Besides, one end of the resistor R4 is electrically connected to the drain and the gate of the sixth transistor MN6, and the other end of the resistor R4 is electrically connected to the output end of the reference voltage circuit REF.

Similar to the embodiment shown in FIG. 1 , the first-stage transconductance amplifier TCA1 and the second-stage transconductance amplifier TCA2 in this embodiment are both class-A output stages, and the third-stage amplifier TSA3 also has a class-A output stage. And class AB output stage, so it can have both the advantages of class A output stage and class AB output stage in circuit design. That is, the components of the first output stage OUT1 are maintained in an on state, and better linearity is disclosed, and at the same time, the second output stage OUT2 can further improve the power efficiency of the third stage amplifier TSA3. Similarly, the first-stage transconductance amplifier TCA1, the second-stage transconductance amplifier TCA2, and the third-stage amplifier TSA3 in this embodiment are also connected in series in a direct coupling manner, and the size ratio between the transistors is determined by special design, so that the overall transimpedance amplifier sensitivity to temperature and different processes can be improved.

Besides, the circuit design of the feedback circuit FB in this embodiment is the same as that of the feedback circuit in the embodiment shown in FIG. gain, wherein the bipolar junction transistor B1 in the feedback circuit FB can achieve the effect of clamping the third output signal TIAp to stabilize the third output signal TIAp.

[Another embodiment of a transimpedance amplifier]

In order to describe the circuit design of the transimpedance amplifier according to the present invention in more detail, another embodiment will be given below for further explanation.

In the following embodiments, parts different from those of the above-described embodiment of FIG. 2 will be described, and the remaining omitted parts are the same as those of the above-described embodiment of FIG. 2 . Also, for convenience of description, like reference numerals or numerals refer to like components.

Please refer to FIG. 3 , which is a circuit diagram of a transimpedance amplifier disclosed in another embodiment of the present invention. The difference from the embodiment shown in FIG. 2 is that in the transimpedance amplifier 3 of the present embodiment, the reference voltage circuit REF further includes a fifth transistor MP5. The fifth transistor MP5 is connected in parallel with the constant current unit I', and is electrically connected between the supply voltage source Vcc and the output end of the constant current unit I'.

Next, please refer to FIG. 4A and FIG. 4B at the same time. FIG. 4A is a graph showing the variation of the reference voltage signal with temperature in the transimpedance amplifier disclosed in the embodiment shown in FIG. 2 , and FIG. 4B is the implementation shown in FIG. 3 . The graph of the reference voltage signal as a function of temperature in the disclosed transimpedance amplifier.

If the temperature changes from -40°C to 125°C, as shown in FIG. 4A , in FIG. 4A , the curve V _m shows the change of the third output signal TIAp of the transimpedance amplifier 3 due to temperature at a low potential, The curve VM shows that the third output signal _TIAp of the transimpedance amplifier 3 is caused by temperature at a high potential, and Ref1 shows the change of the reference voltage signal caused by temperature. On the other hand, as shown in FIG. 4B , in FIG. 4B , the curve V _m shows the change of the third output signal TIAp of the transimpedance amplifier 3 due to the temperature at a low potential, and the curve VM shows the change of the third output signal TIAp of the transimpedance amplifier 3 The third output signal TIAp is a temperature-induced change at a high level, and Ref2 shows a temperature-induced change of the reference voltage signal.

Comparing FIG. 4A with FIG. 4B , it can be known that the voltage change rate of the reference voltage signal of the reference voltage circuit REF in the embodiment shown in FIG. 3 is approximately or equal to the voltage change rate of the third output signal TIAp, but FIG. The voltage change rate of the reference voltage signal of the reference voltage circuit REF in the illustrated embodiment is not the same.

Further description, compared with the reference voltage circuit REF in the embodiment shown in FIG. 2 , the reference voltage circuit REF in the embodiment shown in FIG. 3 additionally sets a fifth transistor MP5, and the fifth transistor MP5 is connected in parallel The constant current unit I' is electrically connected between the supply voltage source Vcc and the output end of the constant current unit I', so that the voltage of the reference voltage signal can be compensated for the voltage change caused by the temperature change. The rate of change is approximately or equal to the rate of change of the voltage of the third output signal, so as to achieve the effect of stabilizing the reference voltage signal.

It should be noted that, the same as the embodiment shown in FIG. 1 and FIG. 2 , the first-stage transconductance amplifier TCA1 and the second-stage transconductance amplifier TCA2 in this embodiment are also class A output stages, and the third The stage amplifier TSA3 also has a class A output stage and a class AB output stage at the same time, so it can have both the advantages of the class A output stage and the class AB output stage in circuit design. That is, the components of the first output stage OUT1 are maintained in an on state, providing better linearity, and at the same time, the second output stage OUT2 can further improve the power efficiency of the third stage amplifier TSA3. Similarly, the first-stage transconductance amplifier TCA1, the second-stage transconductance amplifier TCA2, and the third-stage amplifier TSA3 in this embodiment are also connected in series in a direct coupling manner, and the size ratio between the transistors is determined by special design, so as to improve the overall transimpedance amplifier sensitivity to temperature and different processes.

Besides, the circuit design of the feedback circuit FB in this embodiment is the same as that of the feedback circuit FB in the embodiments shown in FIG. 1 and FIG. 2 , and similarly, the feedback circuit FB can increase the rotation speed of this embodiment The AC gain of the impedance amplifier 3, wherein the bipolar junction transistor B1 in the feedback circuit FB can achieve the effect of clamping the third output signal TIAp to stabilize the third output signal TIAp.

[Possible technical effects of the embodiment]

To sum up, the transimpedance amplifier proposed in the embodiment of the present invention is provided with a third-stage amplifier composed of a first output stage and a second output stage, wherein the circuit design of the first output stage belongs to a class A output stage, In addition, the circuit design of the second output stage belongs to the class AB output stage. In this way, the transimpedance amplifier can have the advantages of both class A amplifiers and class AB amplifiers, and the transmission delay time of the transimpedance amplifier can be shortened. On the other hand, in the reference voltage circuit of the transimpedance amplifier proposed by the embodiment of the present invention, the fifth transistor is arranged in parallel with the constant current unit, and is electrically connected between the supply voltage source and the output end of the constant current unit, In order to improve the instability of the reference voltage signal caused by temperature changes or different process methods.

The above descriptions are merely embodiments of the present invention, which are not intended to limit the patent scope of the present invention.

Claims (6)

1. a transimpedance amplifier, is characterized in that, comprises: A first-stage transconductance amplifier has an input end and an output end. The input end of the first-stage transconductance amplifier is electrically connected to an input current source to receive a first input signal, and then the first-stage transconductance amplifier is sent from the first stage. The output end of the transconductance amplifier outputs a first output signal; a second-stage transconductance amplifier has an input end and an output end, the input end of the second-stage transconductance amplifier is electrically connected to the output end of the first-stage transconductance amplifier to receive the first output signal, and outputting a second output signal from the output end of the second-stage transconductance amplifier; and A third-stage amplifier has an input end and an output end, and the input end of the third-stage amplifier is electrically connected to the output end of the second-stage transconductance amplifier to receive the second output signal, and then the first The output end of the three-stage amplifier outputs a third output signal; a feedback circuit, one end of which is electrically connected to the input end of the first-stage transconductance amplifier, and the other end of which is electrically connected to the output end of the third-stage amplifier to stabilize the third output signal; Wherein, the third-stage amplifier includes: a first output stage, the first output stage including a current source electrically connected to a supply voltage source and the output end of the third-stage amplifier; and A second output stage includes a first NMOS transistor and a second PMOS transistor, the gate of the first NMOS transistor and the second PMOS transistor are connected to form the input terminal of the third-stage amplifier, the second PMOS transistor The source of the transistor is electrically connected to the supply voltage source, the drain of the second PMOS transistor and the drain of the first NMOS transistor are electrically connected to the output end of the third-stage amplifier, and the first NMOS transistor The drain is grounded; When the input current source starts to input current, the current flowing through the first NMOS transistor increases, and at the same time, the current flowing through the second PMOS transistor decreases, so that the voltage value of the third output signal increases. 2. The transimpedance amplifier of claim 1, wherein the feedback circuit comprises: a bipolar junction transistor whose emitter is electrically connected to the input current source, and whose base and collector are connected to the output end of the third-stage amplifier; and A resistor network is connected in parallel with the bipolar junction transistor. 3. The transimpedance amplifier of claim 2, wherein the resistor network is a bridge-connected T-shaped network and a capacitor, the bridge-connected T-shaped network comprises three resistors, and one end of the capacitor is electrically Connected to the bridged T-shaped network, and the other end of the capacitor is grounded. 4 . The transimpedance amplifier of claim 1 , wherein the first-stage transconductance amplifier, the second-stage transconductance amplifier, and the third-stage amplifier are connected in series in a direct coupling manner. 5 . 5 . The transimpedance amplifier of claim 1 , further comprising a reference voltage circuit connected in parallel with the third-stage amplifier, and the reference voltage circuit comprises a certain current unit, a third transistor, a fourth transistor, a fifth transistor, a sixth transistor and a resistor; Wherein, the constant current unit includes a current mirror and a bias current source, the fifth transistor is connected in parallel with the constant current unit and is electrically connected between the supply voltage source and the output end of the reference voltage circuit, the resistor One end of the resistor is electrically connected to the source and gate of the sixth transistor, and the other end of the resistor is electrically connected to the output end of the reference voltage circuit. The third transistor, the fourth transistor and the current mirror are connected to each other. In parallel connection, the drain of the fourth transistor forms the output terminal of the reference voltage circuit to output a reference voltage signal. 6 . The transimpedance amplifier of claim 5 , wherein the voltage change rate of the reference voltage signal is equal to the voltage change rate of the third output signal. 7 .

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