CN107359865B

CN107359865B - Transimpedance amplifier

Info

Publication number: CN107359865B
Application number: CN201610302649.8A
Authority: CN
Inventors: 陈明东; 林惠祯; 王又法
Original assignee: Guangbao Technologies Singapore Private Ltd
Current assignee: Guangbao Technologies Singapore Private Ltd
Priority date: 2016-05-09
Filing date: 2016-05-09
Publication date: 2020-08-14
Anticipated expiration: 2036-05-09
Also published as: CN107359865A

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 transimpedance Amplifier (TIA), and more particularly, to a transimpedance Amplifier (transimpedance Amplifier) for shortening a transmission delay time.

Background

In optical communication systems, the gain and sensitivity of the optical receiver are important characteristics, and both must be improved to optimize the transmission performance. The structure of a Single-Stage transimpedance amplifier adopted by a traditional optical receiver is simple, but the structure of the Single-Stage transimpedance amplifier has the problem that high sensitivity cannot be obtained due to insufficient voltage gain because the overall gain and bandwidth characteristics are closely related to the impedance of the output end of the amplifier.

Therefore, the optical receiver is generally designed by using a Multi-Stage (Multi-Stage) transimpedance amplifier (transimpedance amp) architecture to achieve high voltage gain. The architecture of such a multi-stage transimpedance amplifier usually includes a plurality of single amplifiers connected in series, but since the input current of the optical receiver depends on the infrared rays received by the photodiode, the maximum value and the minimum value of the input current may have a difference of four times. The difference between the maximum and minimum values of the input current will increase the Propagation Delay (Propagation Delay) from high to low at the output of the transimpedance amplifier.

Disclosure of Invention

The embodiment of the invention discloses a transimpedance amplifier which comprises 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, wherein the input end of the first-stage transconductance amplifier is electrically connected to the input current source to receive the first input signal, and the output end of the first-stage transconductance amplifier outputs the first output signal. The second-stage transduction amplifier is provided with an input end and an output end, wherein the input end of the second-stage transduction amplifier is electrically connected with the output end of the first-stage transduction amplifier so as to receive the first output signal, and then the output end of the second-stage transduction amplifier outputs a second output signal. The third-stage amplifier is provided with an input end and an output end, wherein the input end of the third-stage amplifier is electrically connected to the output end of the second-stage transduction amplifier so as to receive the second output signal, and then the output end of the third-stage amplifier outputs a third output signal. One end of the feedback circuit is electrically connected to the input end of the first-stage transduction amplifier, and the other end of the feedback circuit is electrically connected to the output end of the third-stage amplifier so as to stabilize a 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 comprises a current source, one end of which is electrically connected to the supply voltage source to disclose the stable current, and the other end of which is connected to the output terminal 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 first NMOS transistor is connected with the grid electrode of the second PMOS transistor to form the input end 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 embodiment of the invention, the transimpedance amplifier includes a reference voltage circuit. The reference voltage circuit comprises a constant current unit, a third transistor, a fourth transistor and a fifth transistor. The constant current unit comprises a current mirror and a bias current source. The grid electrode of the third transistor, the grid electrode of the fourth transistor and the current mirror are connected in parallel. 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 to the constant current unit and electrically connected between the supply voltage source and the output end of the constant current source.

In summary, the transimpedance amplifier according to the embodiment of the present invention includes the third stage amplifier composed of the first output stage and the second output stage, wherein the circuit design of the first output stage belongs to the configuration of the class a amplifier, and the circuit design of the second output stage belongs to the configuration of the class AB amplifier. On the other hand, in the reference voltage circuit of the transimpedance amplifier according to the embodiment of the present invention, the fifth transistor is disposed in parallel to the constant current unit and electrically connected between the supply voltage source and the output terminal of the reference voltage circuit, so as to improve the instability of the reference voltage signal caused by temperature variation or variation generated in the manufacturing process.

For a better understanding of the nature and technical content of the present invention, reference should be made to the following detailed description of the invention and the accompanying drawings, which are provided for illustration purposes only and are not intended to limit the scope of the invention.

Drawings

Fig. 1 is a circuit diagram of a transimpedance amplifier according to an embodiment of the present invention.

Fig. 2 is a circuit diagram of a transimpedance amplifier according to another embodiment of the present invention.

Fig. 3 is a circuit diagram of a transimpedance amplifier according to another embodiment of the present invention.

Fig. 4A is a graph of the reference voltage signal with temperature variation in the transimpedance amplifier according to the embodiment disclosed in fig. 2.

Fig. 4B is a graph of the reference voltage signal with temperature variation in the transimpedance amplifier according to the embodiment disclosed in fig. 3.

Detailed Description

Various embodiments are described more fully below with reference to the accompanying drawings, in which some embodiments are shown. The inventive concept may, however, 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. In the drawings, like numerals refer to like elements throughout.

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. Thus, a first component discussed below could be termed a second component without departing from the teachings of the present concepts. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

[ embodiments of transimpedance amplifiers ]

Referring to fig. 1, fig. 1 is a circuit diagram of a transimpedance amplifier according to 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, 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 the output end of the first stage transconductance amplifier 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 for receiving the first output signal and outputting a second output signal from the output end of the second-stage transconductance amplifier TCA 2. The third-stage amplifier TSA3 has an input end and an output end, the input end of the third-stage amplifier TSA3 is electrically connected to the output end of the second-stage transconductance amplifier TCA2 to receive the second output signal, and the output end of the third-stage 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 OUT 2.

The following is a teaching to further illustrate the working principle of the transimpedance amplifier 1. As shown in fig. 1, the third stage amplifier TSA3 of the transimpedance amplifier 1 of the present embodiment is composed of a first output stage OUT1 and a second output stage OUT 2. The first output stage OUT1 includes a current source Is, wherein one end of the current source Is electrically connected to the supply voltage source Vcc to disclose a stable current, and the other end of the current source Is connected to the output terminal of the third stage amplifier TSA 3. The second output stage OUT2 includes a first NMOS transistor MN1 and a second PMOS transistor MP 2. The first NMOS transistor MN1 is connected to the gate of the second PMOS transistor MP2 to form an input of the third stage amplifier TSA 3. The source of the second PMOS transistor MP2 is electrically connected to the supply voltage 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 TSA 3. The source of the first NMOS transistor MN1 is grounded. That is, the first output stage OUT1 belongs to a class a output stage, and the second output stage OUT2 belongs to a class AB output stage. In addition, in the present embodiment, the third-stage amplifier TSA3 may further include a second NMOS transistor MN2, as shown in fig. 1, a gate and a source of the second NMOS transistor MN2 are connected to the output terminal of the third-stage amplifier TSA 3.

In the present embodiment, the first output stage OUT1 Is a current source Is connected to a reference voltage source (not shown) for providing a constant stabilizing current. When the input current of the input current source Iin starts to be inputted, 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 bjt B1.

It should be noted that, in the embodiment, since the third stage amplifier TSA3 has both the class a output stage and the class AB output stage, the circuit design advantages of the class a output stage and the class AB output stage can be achieved. That is, the components of the first output stage OUT1 remain turned on, which discloses better linearity, and the second output stage OUT2 further improves the efficiency of the third stage amplifier TSA 3.

On the other hand, in the embodiment, it should be noted that the first-stage transconductance amplifier TCA1 and the second-stage transconductance amplifier TCA2 are class a output stages, and the first-stage transconductance amplifier TCA1, the second-stage transconductance amplifier TCA2 and the third-stage transconductance amplifier TSA3 are connected in series in a direct coupling manner. That is, no capacitor is disposed between the first transconductance amplifier TCA1, the second transconductance amplifier TCA2 and the third transconductance amplifier TSA3, so that the size ratio of the transistors must be specially designed during circuit design, thereby improving the sensitivity of the transimpedance amplifier to temperature and different processes.

In addition, referring to fig. 1 again, the feedback circuit FB in the present embodiment includes a bjt B1 and a resistor network RC. The emitter of the bjt B1 is electrically connected to the input current source Iin, and the base and the collector of the bjt B1 are connected to the output terminal of the third-stage amplifier TSA 3. In addition, the resistor network RC is connected in parallel to the bjt B1, and includes a bridge T-network formed by three resistors R1-R3 and a capacitor C1, wherein one end of the capacitor C1 is electrically connected to the bridge T-network, and the other end of the capacitor C1 is grounded. To explain, the feedback circuit FB can increase the gain of the transimpedance amplifier 1 of the present embodiment, wherein the bjt 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 ]

To describe the circuit design of the transimpedance amplifier according to the present invention in more detail, an embodiment will be described in further detail.

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

Referring to fig. 2, fig. 2 is a circuit diagram of a transimpedance amplifier according to another embodiment of the present invention. The difference between the embodiment shown in fig. 1 and the above-mentioned embodiment is that in the present embodiment, the transimpedance amplifier 2 further includes a reference voltage circuit, which is connected in parallel to the third stage amplifier TSA3, and includes a constant current unit I', a third transistor 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, 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. In addition, 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 terminal of the reference voltage circuit REF.

As with the embodiment shown in fig. 1, the first transconductance amplifier TCA1 and the second transconductance amplifier TCA2 of the present embodiment are class a output stages, and the third transconductance amplifier TSA3 has both class a and class AB output stages, so that the circuit design advantages of the class a and class AB output stages can be achieved. That is, the devices of the first output stage OUT1 remain turned on, which discloses better linearity, while the second output stage OUT2 further improves the power efficiency of the third stage amplifier TSA 3. Similarly, the first transconductance amplifier TCA1, the second transconductance amplifier TCA2 and the third transconductance amplifier TSA3 of the present embodiment are also connected in series in a direct coupling manner, and the size ratio between the transistors is specially designed, so that the sensitivity of the whole transimpedance amplifier to temperature and different processes can be improved.

Besides, the circuit design of the feedback circuit FB in the present embodiment is the same as that of the embodiment shown in fig. 1, and similarly, the feedback circuit FB can increase the gain of the transimpedance amplifier 2 of the present embodiment, wherein the bjt 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 the following embodiment, portions different from those of the above-described embodiment of fig. 2 will be described, and the remaining omitted portions are the same as those of the above-described embodiment of fig. 2. Also, for convenience of explanation, like reference numerals or signs refer to like components.

Referring to fig. 3, fig. 3 is a circuit diagram of a transimpedance amplifier according to another embodiment of the present invention. The difference between the above-mentioned 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 MP 5. The fifth transistor MP5 is connected in parallel to the constant current unit I 'and is electrically connected between the supply voltage source Vcc and the output terminal of the constant current unit I'.

Next, referring to fig. 4A and fig. 4B, fig. 4A is a graph of the reference voltage signal of the transimpedance amplifier disclosed in the embodiment shown in fig. 2 varying with temperature, and fig. 4B is a graph of the reference voltage signal of the transimpedance amplifier disclosed in the embodiment shown in fig. 3 varying with temperature.

If the temperature change is-40C to 125C, as shown in FIG. 4A, curve V_mShows the temperature variation of the third output signal TIAP of the transimpedance amplifier 3 at the low potential, curve V_MThe third output signal TIAp of the transimpedance amplifier 3 is shown at a high potential due to temperature, and Ref1 shows the change in the reference voltage signal due to temperature. On the other hand, as shown in FIG. 4B, curve V_mThe change of the third output signal TIAp of the transimpedance amplifier 3 due to temperature is shown at a low potential, the change of the third output signal TIAp of the transimpedance amplifier 3 due to temperature is shown at a high potential, and Ref2 shows the change of the reference voltage signal due to temperature.

Comparing fig. 4A and fig. 4B, it can be seen 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 equal to or equal to the voltage change rate of the third output signal TIAp, but the voltage change rate of the reference voltage signal of the reference voltage circuit REF in the embodiment shown in fig. 2 is not.

Further, compared to 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 includes a fifth transistor MP5, and the fifth transistor MP5 is connected in parallel to the constant current unit I 'and electrically connected between the supply voltage source Vcc and the output terminal of the constant current unit I', so that the voltage change rate of the reference voltage signal can be approximated or equal to the voltage change rate of the third output signal by compensating the voltage change caused by the temperature change, thereby achieving the effect of stabilizing the reference voltage signal.

It should be noted that, as in the embodiment shown in fig. 1 and fig. 2, the first-stage transconductance amplifier TCA1 and the second-stage transconductance amplifier TCA2 of the present embodiment are both class a output stages, and the third-stage transconductance amplifier TSA3 has both class a output stages and class AB output stages, so that the circuit design advantages of the class a output stages and the class AB output stages can be achieved. That is, the components of the first output stage OUT1 remain turned on, which discloses better linearity, while the second output stage OUT2 further improves the power efficiency of the third stage amplifier TSA 3. Similarly, the first transconductance amplifier TCA1, the second transconductance amplifier TCA2 and the third transconductance amplifier TSA3 of the present embodiment are also connected in series in a direct coupling manner, and the size ratio between the transistors is specially designed, so that the sensitivity of the whole transimpedance amplifier to temperature and different processes can be improved.

Besides, the circuit design of the feedback circuit FB in the present embodiment is the same as the feedback circuit FB in the embodiment shown in fig. 1 and fig. 2, and similarly, the feedback circuit FB can increase the ac gain of the transimpedance amplifier 3 of the present embodiment, wherein the bjt 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 ]

In summary, the transimpedance amplifier according to the embodiment of the present invention includes the third stage amplifier composed of the first output stage and the second output stage, wherein the circuit design of the first output stage belongs to the class a output stage, and the circuit design of the second output stage belongs to the class AB output stage. On the other hand, in the reference voltage circuit of the transimpedance amplifier according to the embodiment of the present invention, the fifth transistor is disposed in parallel to the constant current unit and electrically connected between the supply voltage source and the output terminal of the constant current unit, so as to improve instability of the reference voltage signal caused by temperature variation or different process methods.

The above description is only an example of the present invention, and is not intended to limit the scope of the present invention.

Claims

1. A transimpedance amplifier, comprising:

the first-stage transduction amplifier is provided with an input end and an output end, wherein the input end of the first-stage transduction amplifier is electrically connected with an input current source so as to receive a first input signal, and then the output end of the first-stage transduction amplifier outputs a first output signal;

the second-stage transduction amplifier is provided with an input end and an output end, the input end of the second-stage transduction amplifier is electrically connected with the output end of the first-stage transduction amplifier so as to receive the first output signal, and then the output end of the second-stage transduction amplifier outputs a second output signal; and

a third-stage amplifier having an input end and an output end, the input end of the third-stage amplifier being electrically connected to the output end of the second-stage transduction amplifier for receiving the second output signal, and the output end of the third-stage amplifier outputting a third output signal;

one end of the feedback circuit is electrically connected to the input end of the first-stage transduction amplifier, and the other end of the feedback circuit is electrically connected to the output end of the third-stage amplifier so as to stabilize the third output signal;

wherein the third stage amplifier comprises:

a first output stage including a current source electrically connected to a supply voltage source and the output terminal of the third stage amplifier; and

a second output stage including a first NMOS transistor and a second PMOS transistor, the gates of the first and second NMOS transistors being connected to form the input terminal of the third stage amplifier, the source of the second PMOS transistor being electrically connected to the supply voltage source, the drain of the second PMOS transistor and the drain of the first NMOS transistor being electrically connected to the output terminal of the third stage amplifier, and the drain of the first NMOS transistor being grounded;

when the input current source starts to input current, the current flowing through the first NMOS transistor increases, and the current flowing through the second PMOS transistor decreases at the same time, so that the voltage value of the third output signal increases.

2. The transimpedance amplifier according to claim 1, wherein the feedback circuit comprises:

a bipolar junction transistor, the emitter of which is electrically connected to the input current source, and the base and the collector of which are connected to the output end of the third-stage amplifier; and

a resistor network connected in parallel to the BJT.

3. The transimpedance amplifier according to claim 2, wherein the resistor network is a bridge T-network and a capacitor, the bridge T-network comprising three resistors, one end of the capacitor being electrically connected to the bridge T-network and the other end of the capacitor being grounded.

4. The transimpedance amplifier according to claim 1, wherein said first transconductance amplifier, said second transconductance amplifier and said third transconductance amplifier are connected in series by direct coupling.

5. The transimpedance amplifier according to claim 1, further comprising a reference voltage circuit connected in parallel to the third stage amplifier, the reference voltage circuit comprising a constant current unit, a third transistor, a fourth transistor, a fifth transistor, a sixth transistor and a resistor;

the constant current unit comprises 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, one end of the resistor is electrically connected with the source electrode and the grid electrode of the sixth transistor, the other end of the resistor is electrically connected with the output end of the reference voltage circuit, the third transistor, the fourth transistor and the current mirror are connected in parallel, and the drain electrode of the fourth transistor forms the output end of the reference voltage circuit so as to output a reference voltage signal.

6. The transimpedance amplifier according to claim 5, wherein a voltage rate of change of the reference voltage signal is equal to a voltage rate of change of the third output signal.