A push-pull drive circuit and optical communication device

Abstract

This application discloses a push-pull driving circuit and an optical communication device, relating to the field of integrated circuit technology. Specifically, it includes a push-pull driving module and a transconductance feedback module. The push-pull driving module receives input signals and generates driving current. The transconductance feedback module is electrically connected to the push-pull driving module and includes transconductance units and feedback units connected in parallel. The input terminal of the transconductance unit is connected to the output terminal of the push-pull driving module, and the output terminal is connected to an optoelectronic load. The feedback unit is connected across the two ends of the transconductance unit. This application isolates the parasitic output capacitance of the push-pull driving module from the parasitic capacitance of the optoelectronic load through the transconductance feedback module, separating the large dominant poles at the input and output nodes of the transconductance feedback module. By employing a push-pull driving module and eliminating the original virtual load, it solves the technical problems of low-frequency large poles limiting bandwidth and high static power consumption in traditional driving circuits.

Description

Technical Field

[0001] This application relates to the field of integrated circuit technology, and in particular to a push-pull drive circuit and an optical communication device. Background Technology

[0002] As a crucial electro-optical conversion module in optical signal links, the optical transmitter is vital to the overall performance of the optical signal link. Among optical devices, vertical-cavity surface-emitting lasers (VCSELs) occupy an important position in short-distance optical interconnect communication due to their advantages such as low power consumption, high energy efficiency, low temperature drift, high modulation bandwidth, and excellent beam quality.

[0003] In existing technologies, optical transmitters typically employ conventional current-mode logic common-source driver circuits or conventional current-mode push-pull driver circuits to achieve electro-optic modulation. The conventional current-mode logic common-source driver circuit mainly comprises a differential input, a single-ended output current-mode logic common-source amplifier stage, a bias current generation circuit, and a vertical-cavity surface-emitting laser as a load. The tail current source magnitude is modulated by a control signal, and the dummy load is used to match the impedance of the other output of the differential pair and provide an AC discharge path when the input is logic low.

[0004] However, the aforementioned existing technologies have the following drawbacks: On the one hand, in traditional current-mode logic common-source drive circuits, when the input signal is low, the driver's tail current flows through the virtual load instead of driving the VCSEL load, resulting in half of the dynamic current energy being dissipated in the virtual load, generating additional static power consumption and leading to low overall circuit energy efficiency. On the other hand, whether it is a traditional current-mode logic common-source drive circuit or a push-pull drive circuit, its output node not only includes the parasitic effects of the drive circuit itself, but also the parasitic effects of the bias current generation circuit and the VCSEL device. These multiple parasitic effects are superimposed on the output node, introducing a low-frequency dominant pole. This low-frequency dominant large pole leads to a significant deficiency in the system's electro-optic bandwidth, resulting in a large deterministic jitter and a small eye height in the output optical signal eye diagram.

[0005] In summary, the aim of this art is to propose a VCSEL driver circuit with high energy efficiency and high modulation bandwidth, which can effectively overcome the parasitic effect of large poles at the output node. Summary of the Invention

[0006] The main objective of this application is to provide a push-pull drive circuit and an optical communication device, which aims to solve the problem of low energy efficiency of current-mode logic common-source drive circuits, and also to solve the problem of limited system bandwidth and degraded eye diagram caused by the presence of dominant large poles in the output nodes of existing drive circuits.

[0007] To achieve the above objectives, this application proposes a push-pull drive circuit, comprising: The push-pull driver module is used to receive input signals and generate drive current; A transconductance feedback module, electrically connected to the push-pull drive module, includes: A transconducting unit, the input of which is electrically connected to the output of the push-pull drive module, and the output of which is used to connect to an optoelectronic load; The feedback unit has a first terminal electrically connected to the output terminal of the transconductance unit and a second terminal electrically connected to the input terminal of the transconductance unit. The transconductance unit and the feedback unit are connected in parallel to isolate the parasitic capacitance of the push-pull drive module from the parasitic capacitance of the optoelectronic load.

[0008] Furthermore, the push-pull drive module includes: A pull-up drive circuit, the control terminal of which is used to receive the input signal, and the first terminal of which is used to connect to a power supply; A pull-down drive circuit, whose control terminal is used to receive the input signal, whose first terminal is grounded and whose second terminal is electrically connected to the second terminal of the pull-up drive circuit; The common contact of the pull-up drive circuit and the pull-down drive circuit is also electrically connected to the input terminal of the transconductance feedback module to output the drive current to the transconductance feedback module.

[0009] Furthermore, the pull-down drive circuit includes: The first transistor has its first terminal grounded; The second transistor has its first terminal electrically connected to the second terminal of the first transistor, and its second terminal electrically connected to the input terminal of the transconductance feedback module. The pull-up drive circuit includes a third transistor and a fourth transistor; The third transistor has its first terminal electrically connected to the second terminal of the fourth transistor, and its second terminal electrically connected to the second terminal of the second transistor. The first terminal of the fourth transistor is connected to a power source. The input signal is connected to the control terminal of the first transistor or the control terminal of the second transistor; the input signal is connected to the control terminal of the third transistor or the control terminal of the fourth transistor.

[0010] Furthermore, the control terminals of both the first transistor and the fourth transistor are used to receive the input signal; Both the control terminal of the second transistor and the control terminal of the third transistor are used to receive bias voltage.

[0011] Furthermore, the transconductance unit includes at least one transconductance transistor; The control terminal of the transconductance transistor serves as the input terminal of the transconductance unit, used to receive the drive current output by the push-pull drive module, and generate a control voltage based on the drive current. The controlled terminal of the transconductance transistor serves as the output terminal of the transconductance unit, and is used to output a modulated current to the opto-load according to the control voltage.

[0012] Furthermore, the transconductance unit includes: The fifth transistor has its first terminal grounded; The sixth transistor has its first terminal connected to a power source and its second terminal electrically connected to the second terminal of the fifth transistor to form the output terminal of the transconductance unit. The control terminals of the fifth transistor and the sixth transistor are connected together to form the input terminal of the transconductance unit.

[0013] Furthermore, the feedback unit is a feedback resistor; The feedback resistor is connected between the input and output terminals of the transconductance unit to reduce the equivalent input impedance and equivalent output impedance of the transconductance feedback module.

[0014] Furthermore, the resistance value of the feedback resistor is matched with the transconductance value of the transconductance unit, so that the equivalent input impedance and equivalent output impedance of the transconductance feedback module are both less than the output equivalent resistance of the push-pull drive module.

[0015] Furthermore, it also includes a bias current generation circuit, the output of which is electrically connected to the output of the transconductance feedback module, for providing DC bias current to the optoelectronic load.

[0016] This application also discloses an optical communication device, comprising: Vertical cavity surface-emitting laser; The push-pull drive circuit described above; The push-pull drive circuit is used to provide modulation current for the vertical cavity surface-emitting laser.

[0017] The above technical solution has the following advantages: This application electrically connects a transconductance feedback module between the output of the push-pull drive module and the opto-load. The transconductance feedback module includes a parallel transconductance unit and a feedback unit, which isolates the parasitic capacitance of the push-pull drive module's output from the parasitic capacitance of the opto-load. This separates the large dominant pole at the input and output nodes of the transconductance feedback module, thus solving the problem of low-frequency dominant maxima and limited high-frequency bandwidth caused by the superposition effect of parasitic capacitance at a single output node in traditional drive circuits. Furthermore, this application eliminates the original virtual load, improves energy efficiency, and decomposes the dominant large pole into two extremely high-frequency secondary dominant poles, significantly improving the electro-optic modulation bandwidth and eye diagram quality of the system. Attached Figure Description

[0018] The present application will now be described in detail with reference to specific embodiments and accompanying drawings, wherein: Figure 1 This is a structural block diagram of this application; Figure 2 This is a schematic diagram of a traditional current-mode logic common-source driver. Figure 3 The diagram shows the energy efficiency of a conventional current-mode logic common-source driver (a) and a conventional current-mode push-pull driver (b). Figure 4 This is the equivalent schematic diagram of a traditional current-mode push-pull driver. Figure 5 This is the equivalent schematic diagram of the current-mode push-pull driver based on the Cherry-Hopper structure in this application; Figure 6 This is a schematic diagram of the push-pull drive circuit of this application; Figure 7 The bandwidth response diagrams are shown for a conventional current-mode common-source driver and that of this application. Figure 8 Transient eye diagrams for a conventional current-mode push-pull driver (a) and a current-mode push-pull driver of this application (b).

[0019] In the diagram: 10. Push-pull drive module; 11. Pull-up drive circuit; 12. Pull-down drive circuit; 20. Transconductance feedback module; 21. Transconductance unit; 22. Feedback unit; 30. Opto-load; 40. Bias current generation circuit; M1, the first transistor; M2, the second transistor; M3, the third transistor; M4, the fourth transistor; M5, the fifth transistor; M6, the sixth transistor. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the following specific embodiments are merely illustrative of this application and do not constitute a limitation thereof.

[0021] In short-range optical interconnect communication systems, the driver circuit of the optical transmitter determines the overall transmission quality of the optical signal link. Traditional current-mode logic common-source driver circuits, when the input signal is low, cause the driver's tail current to flow through the virtual load, resulting in nearly half of the dynamic current energy being ineffectively dissipated, leading to low energy utilization efficiency. Specifically, for example… Figure 2 As shown. Furthermore, the single output node of a traditional driver circuit not only includes the parasitic capacitance of the driver itself, but also the parasitic capacitance of the bias current generation circuit 40 and the vertical-cavity surface-emitting laser load. This huge total parasitic capacitance, combined with the output impedance, introduces a low-frequency dominant pole at the output, severely limiting the system's opto-modulation bandwidth and causing eye diagram degradation of the output optical signal, such as... Figure 4 As shown.

[0022] Based on the aforementioned problems in the prior art, this application provides a push-pull drive circuit and an optical communication device, which aims to achieve mutual isolation between the parasitic capacitance at the input end and the parasitic capacitance at the output end through improvements in circuit topology, thereby solving the problem of large pole limitation and improving current utilization.

[0023] To facilitate understanding of the technical solution of this application, the following key terms are clearly defined: Control terminal and controlled terminal: In the semiconductor device involved in this embodiment, when the transistor is a field-effect transistor (such as a MOSFET), the control terminal refers to the gate, and the controlled terminal and its corresponding first terminal and second terminal refer to the source and drain. When the transistor is a bipolar junction transistor (such as a BJT), the control terminal refers to the base, and the controlled terminal and its corresponding first terminal and second terminal refer to the emitter and collector.

[0024] Drive current and modulation current: Drive current is the original current signal generated based on the input signal conversion; modulation current refers to the current signal that is finally injected into the photoelectric load 30 to drive it to emit light after being transformed and amplified by the transconductance feedback module 20.

[0025] like Figure 1 , Figure 5 and Figure 6 As shown, this embodiment provides a push-pull drive circuit, which mainly includes a push-pull drive module 10 and a transconductance feedback module 20; The input terminal of the push-pull drive module 10 is used to receive externally transmitted input signals and generate corresponding drive currents based on the input signals; the transconductance feedback module 20 is electrically connected to the output terminal of the push-pull drive module 10 and is used for impedance transformation and signal transmission.

[0026] The transconductance feedback module 20 includes a transconductance unit 21 and a feedback unit 22. The input terminal of the transconductance unit 21 is electrically connected to the output terminal of the push-pull drive module 10, and its output terminal is used to connect to an external optoelectronic load 30. The first terminal of the feedback unit 22 is electrically connected to the output terminal of the transconductance unit 21, and its second terminal is electrically connected to the input terminal of the transconductance unit 21. The transconductance unit 21 and the feedback unit 22 form a parallel structure in the circuit, thereby isolating the parasitic capacitance of the push-pull drive module 10 from the parasitic capacitance of the optoelectronic load 30.

[0027] In some embodiments, the push-pull drive module 10 is not limited to a specific MOS transistor stack structure; any logic circuit that can respond to the input signal and alternately provide pull-up and pull-down currents can be used.

[0028] In the transconductance feedback module 20, the transconductance unit 21 can be selected as a single-stage or multi-stage active amplification device, and the feedback unit 22 can be selected as a passive impedance element or an active impedance element; there are no specific limitations here.

[0029] like Figure 4 and Figure 5 As shown, Figure 4 For traditional push-pull drive circuits, due to the parasitic nature of the drive circuit itself... Parasitic capacitance of opto-load 30 and bias circuit Directly superimposed on a single output node, resulting in equivalent capacitance Extremely large, and the equivalent resistance of the output node This introduces a low-frequency dominant large pole at the output node. Low-frequency dominant large poles This is the root cause of the deterioration in system bandwidth. At this point, the modulation current of the opto-load 30... for:

[0030] like Figure 5 As shown, this embodiment introduces a parallel transconductance unit 21 and a feedback unit 22. The transconductance unit 21 adopts... It is indicated that the feedback unit 22 adopts This means that the output parasitic capacitance of the push-pull drive module 10 is limited to the input node of the transconductance unit 21, thereby separating the original large parasitic capacitance to the input and output nodes of the transconductance feedback module 20, reducing the large parasitic capacitance that was originally concentrated at a single node. Parasitic capacitance at the input of the transconductance feedback module 20 and parasitic capacitance at the output terminal This avoids the situation where multiple capacitors overlap, leading to a single node exhibiting a low-frequency dominant large pole. This embodiment not only avoids the power consumption problem of traditional virtual loads and improves energy utilization, but also divides a single low-frequency dominant node into two high-frequency poles, significantly improving the system's bandwidth and eye diagram opening.

[0031] like Figure 6 As shown in one embodiment of this application, the push-pull drive module 10 specifically includes a pull-up drive circuit 11 and a pull-down drive circuit 12. The control terminal of the pull-up drive circuit 11 is used to receive the input signal, and its first terminal is connected to a power supply. The control terminal of the pull-down drive circuit 12 is used to receive the input signal, its first terminal is grounded, and its second terminal is electrically connected to the second terminal of the pull-up drive circuit 11. The common connection point of the pull-up drive circuit 11 and the pull-down drive circuit 12 is also electrically connected to the input terminal of the transconductance feedback module 20 to output the drive current to the transconductance feedback module 20.

[0032] In some embodiments, the pull-up drive circuit 11 and the pull-down drive circuit 12 can employ complementary semiconductor switching devices, such as a combination of PMOS and NMOS transistors, as long as the control terminals of the pull-up drive circuit 11 and the pull-down drive circuit 12 are alternately turned on. When the control terminal of the pull-up drive circuit 11 is turned on, it outputs a high-level signal to the transconductance feedback module 20, at which time the pull-down drive circuit 12 is turned off; when the control terminal of the pull-down drive circuit 12 is turned on, it outputs a low-level signal to the transconductance feedback module 20, at which time the pull-up drive circuit 11 is turned off.

[0033] like Figure 3 As shown, combined with Figure 3 (a) and Figure 3 (b) Comparison, Figure 3 (a) is a common-source driver for traditional current-mode logic (CML). Figure 3 (b) is a current-mode push-pull driver; in Figure 3 (a) In a traditional CML common-source driver, the tail current can only be used to drive the optoload 30 when IN is high, while when IN is low, the tail current flows through the dummy load; when driving the optoload 30, this results in half of the dynamic current energy being dissipated in the dummy load; Figure 3 (b) In a traditional current-mode push-pull driver, when the input signal IN is high, the pull-down path is activated, and the current of the opto-load 30 is... The current flows to ground. When the input signal IN is low, the pull-up path is activated, and at this time, the current in VDD flows to ground. The size of the flow direction to the photoelectric load is 30; the following is the calculation method of this embodiment: like Figure 3(a) It can be seen that the current flowing through the photoelectric load 30 is Then we have:

[0034] in, The bias voltage applied to the photoelectric load 30; bias voltage It provides current to the opto-load 30 and also to the virtual load.

[0035] From the above expression (2), we can derive expression (3), at which point the actual bias voltage of the photoelectric load 30 is... for:

[0036] like Figure 3 (b) It can be seen that the current flowing through the opto-load 30 in the current-mode push-pull driver is Then we have:

[0037] From expression (4), it can be seen that the bias current of the photoelectric load 30 at this time is Therefore, combining Figure 3 (a) and Figure 3 (b) As can be seen from the comparison, the traditional CML common-source driver structure not only sacrifices dynamic power consumption during signal modulation, but also sacrifices... And the static power consumption corresponding to the voltage product; therefore, in terms of energy efficiency, this embodiment... Figure 3 The power consumption of the push-pull output structure in (b) is much lower than that of the traditional CML common-source driver. This embodiment completely eliminates the useless power dissipated on the virtual load in the traditional circuit, so that all the modulation current generated by the push-pull drive circuit is used to drive the optoelectronic load 30, realizing the full utilization of the modulation current energy.

[0038] like Figure 5 and Figure 6As shown, in one embodiment, the pull-down drive circuit 12 includes a first transistor M1 and a second transistor M2. The first terminal of the first transistor M1 is grounded, the first terminal of the second transistor M2 is electrically connected to the second terminal of the first transistor M1, and the second terminal of the second transistor M2 is electrically connected to the input terminal of the transconductance feedback module 20. The pull-up drive circuit 11 includes a third transistor M3 and a fourth transistor M4. The first terminal of the third transistor M3 is electrically connected to the second terminal of the fourth transistor M4, and the second terminal of the third transistor M3 is electrically connected to the second terminal of the second transistor M2. The first terminal of the fourth transistor M4 is connected to a power supply. The control terminal of the first transistor M1 or the control terminal of the second transistor M2 is connected to the input signal. The control terminal of the third transistor M3 or the control terminal of the fourth transistor M4 is connected to the input signal.

[0039] In some embodiments, the first transistor M1, the second transistor M2, the third transistor M3, and the fourth transistor M4 are preferably high-frequency field-effect transistors, such as PMOS transistors or NMOS transistors. In this embodiment, the first transistor M1 and the second transistor M2 are preferably NMOS transistors, and the third transistor M3 and the fourth transistor M4 are preferably PMOS transistors. Of course, the first transistor M1 and the second transistor M2 can also be PMOS transistors, and the third transistor M3 and the fourth transistor M4 can be NMOS transistors. The selection is made according to the needs of the scenario. Since the first transistor M1 and the second transistor M2 together form the pull-down drive circuit 12, and the third transistor M3 and the fourth transistor M4 together form the pull-up drive circuit 11, it is only necessary to select one of the first transistor M1 and the second transistor M2 to connect the input signal to the control terminal.

[0040] In this embodiment, the control terminals of the first transistor M1 and the fourth transistor M4 are preferably used to receive high-frequency input signals as dynamic switching elements; while the control terminals of the second transistor M2 and the third transistor M3 are preferably used to receive DC bias voltage as common-gate voltage regulation and isolation elements to reduce the impact of Miller effect on the input capacitance and improve the output impedance, thus ensuring the integrity of the high-frequency signal. In this embodiment, the bias voltage is configured by a digital-to-analog converter circuit, so that the push-pull drive module 10 can provide a stable and precisely adjustable drive current in the high-speed switching state.

[0041] Combining expressions (2), (3), and (4), it can be seen that the actual bias voltage of this application after passing through the photoelectric load 30 is... The CML common source driver structure, rather than the transmission, still exists. Dynamic power consumption, thereby improving energy utilization.

[0042] like Figure 6As shown, in one embodiment of this application, the transconductance unit 21 includes at least one transconductance transistor; the control terminal of the transconductance transistor serves as the input terminal of the transconductance unit 21, and is used to receive the driving current output by the push-pull driving module 10, and generate a control voltage based on the driving current; the controlled terminal of the transconductance transistor serves as the output terminal of the transconductance unit 21, and is used to output a modulation current to the optoelectronic load 30 according to the control voltage.

[0043] In some embodiments, the transconductance unit 21 may use only a single NMOS or PMOS transistor as a common source amplifier, or it may use multiple transistors as a common source amplifier. After the drive current output by the push-pull drive module 10 flows into the input terminal of the transconductance unit 21, a fluctuating control voltage is generated by combining the equivalent input impedance of the input terminal node of the transconductance unit 21. The transconductance transistor generates a corresponding current amplification effect at its controlled terminal through the control voltage, thereby outputting the final load modulation current to the opto-load 30.

[0044] like Figure 5 and Figure 6 As shown, in a preferred embodiment of the transconductance unit 21, the transconductance unit 21 includes a fifth transistor M5 and a sixth transistor M6. The first terminal of the fifth transistor M5 is grounded, the first terminal of the sixth transistor M6 is connected to a power supply, and the second terminal is electrically connected to the second terminal of the fifth transistor M5 to form the output terminal of the transconductance unit 21. The control terminal of the fifth transistor M5 and the control terminal of the sixth transistor M6 are connected together to form the input terminal of the transconductance unit 21.

[0045] In some embodiments, this embodiment employs a fifth transistor M5 and a sixth transistor M6 to complement each other in order to form a larger transconductance output.

[0046] The function of the fifth transistor M5 and the sixth transistor M6 is to amplify the voltage signal after impedance conversion at the front-end node back into a modulated current and inject it into the optoload 30. In practical applications, designers can directly adjust the system gain by adjusting the size of the fifth transistor M5 and the sixth transistor M6. This results in a flatter frequency response, higher bandwidth, and significantly improved eye opening while maintaining the same modulation current for driving the opto-load 30.

[0047] like Figure 5 As shown in Figure 6, in one embodiment, the feedback unit 22 is a feedback resistor; the feedback resistor is connected between the input and output terminals of the transconductance unit 21 to reduce the equivalent input impedance and equivalent output impedance of the transconductance feedback module 20.

[0048] In some embodiments, the feedback unit 22 and the transconductance unit 21 together constitute a Cherry-Hopper structure, and the optoelectronic load 30 is preferably a vertical-cavity surface-emitting laser (VCSEL). Since this embodiment reduces the equivalent input impedance and equivalent output impedance of the transconductance feedback module 20, the specific analysis is as follows: like Figure 5 It can be seen that the equivalent input impedance of the Cherry-Hopper is... :

[0049] in, The impedance of feedback unit 22, For the transconductance of transconductance unit 21, The impedance of the opto-load is 30.

[0050] Equivalent output impedance :

[0051] Based on a Cherry-Hopper current-mode push-pull driver architecture, the modulation current of the opto-load 30 is... It can be represented as:

[0052] A comprehensive analysis of formulas (1) to (7) shows that the modulation current supplied to the photoelectric load 30 is approximately equal (e.g., when configured...). Under the condition of (time), the formula It can be approximately simplified to:

[0053] Expression (5) can be approximately simplified to:

[0054] A comprehensive analysis of expressions (6), (8) and (9) shows that, when the modulation current driving the optoelectronic load 30 is approximately equal, the input impedance and output impedance of the Cherry-Hopper structure are significantly smaller than those of the traditional current-mode push-pull driver. Furthermore, since the parasitic capacitances of the input and output nodes are smaller than those of the traditional current-mode push-pull driver, the Cherry-Hopper structure can decompose the dominant large pole of the traditional structure into two non-dominant poles with higher frequencies, thereby increasing the system bandwidth and improving the eye diagram quality.

[0055] like Figure 7 and Figure 8 As shown, in this embodiment, due to the reduced impedance of the input and output nodes, and in conjunction with parasitic capacitance... and Isolated by the transconductance feedback module 20, the large pole at the output of the traditional driver is successfully decomposed into two small poles at higher frequencies, such as... Figure 7 The bandwidth response graphs are compared, with the horizontal axis representing frequency (Hz) and the vertical axis representing gain (dB). The graphs show that the conventional circuit has a smaller 3dB bandwidth for both electrical and optical outputs. For example, the second and fourth curves from top to bottom at 2.00E+10 represent the conventional optical and electrical outputs, respectively. The first and third curves from top to bottom at 2.00E+10 represent the optical and electrical outputs of the current-mode push-pull output driver architecture of this application, respectively. It can be seen that the frequency response curves for the optical and electrical outputs of this application are significantly flatter, and the 3dB cutoff frequency extends significantly to the right (e.g., ...). Figure 7 (the position of the pentagram in the middle) Figure 7 In the optical output (CH) and electrical output (CH) shown, the CH in parentheses refers to the current-mode push-pull driver architecture of Cherry-Hopper mentioned in this application.

[0056] like Figure 8 As shown, Figure 8 (a) is the transient eye diagram of a traditional current-mode push-pull driver under a 50 Gb / s NRZ signal. Figure 8 (b) is the transient eye diagram of the current-mode push-pull driver based on the Cherry-Hopper structure in this application under a 50 Gb / s NRZ signal. Traditional current-mode push-pull drivers suffer from large deterministic jitter and small eye height in the eye diagram due to insufficient bandwidth. However, the driver of this invention based on Cherry-Hopper, thanks to the effective improvement in bandwidth, has significantly reduced eye jitter, significantly increased eye height, and smoother and wider eye opening, demonstrating the effectiveness of the Cherry-Hopper structure in improving signal integrity in short-pitch VCSEL optical interconnect applications.

[0057] like Figure 6 As shown, in one embodiment, the resistance value of the feedback resistor is matched with the transconductance value of the transconductance unit 21, so that the equivalent input impedance and equivalent output impedance of the transconductance feedback module 20 are both less than the output equivalent resistance of the push-pull drive module 10.

[0058] In some embodiments, the value of the feedback resistor is not arbitrarily set, but is matched with the total transconductance of the transconductance unit 21. Through specific size design and resistance value selection, the equivalent input impedance and equivalent output impedance of the transconductance feedback module 20 after closed-loop are significantly smaller than the original equivalent output resistance of the push-pull drive module 10. As can be seen from expressions (6), (8) and (9), when the modulation current driving the optoelectronic load 30 is approximately equal, the input impedance and output impedance of the Cherry-Hopper structure are significantly smaller than the impedance of the traditional current-mode push-pull driver. This has been derived above and will not be described in detail here. Since the expression It is known that the pole frequency is inversely proportional to the product of the node impedance and the node capacitance. When the parasitic capacitance of the input and output nodes is reduced by isolation, and the equivalent impedance of the input and output nodes is reduced by the transconductance feedback module 20, the originally low-frequency dominant large pole is decomposed into two secondary dominant poles located at higher frequencies, which greatly broadens the -3dB bandwidth of the system.

[0059] like Figure 6 As shown, in one embodiment of this application, the embodiment further includes a bias current generation circuit 40, the output terminal of which is electrically connected to the output terminal of the transconductance feedback module 20, for providing DC bias current to the optoelectronic load 30.

[0060] In some embodiments, the output of the bias current generation circuit 40 is directly electrically connected to the output of the transconductance feedback module 20 via a wire or metal trace. The bias current generation circuit 40 provides a basic DC bias current for the optoelectronic load 30 such as the vertical cavity surface-emitting laser, ensuring that the laser always operates in the linear emission region above the threshold current.

[0061] In the normal signal flow, the external input signal and the bias voltage jointly drive the push-pull drive module 10 to conduct alternately. The generated drive current is converted into a high-frequency voltage at the input node of the transconductance feedback module 20, and then drives the photoelectric load 30 to emit light through the transconductance unit 21.

[0062] This application also discloses an optical communication device that integrates a vertical cavity surface-emitting laser and a push-pull driver circuit, wherein the push-pull driver circuit is used to provide modulation current to the vertical cavity surface-emitting laser.

[0063] This embodiment overcomes the limitations of low-frequency large poles in the drive architecture. By adopting a combination of push-pull and Cherry-Hopper structures, the overall optical signal link not only achieves extremely high energy efficiency in short-distance optical interconnect communication, but also obtains an eye diagram with lower jitter, thus improving the effectiveness of signal integrity enhancement in short-distance VCSEL optical interconnect applications.

[0064] Working principle: When the system starts working, the high-speed differential electrical signal (i.e., the input signal, corresponding to) from the front-end circuitry. Figure 6 The IN port first enters the input terminal of the push-pull drive module 10. At this time, the digital-to-analog converter (DAC) outputs a stable bias voltage (such as...). Figure 6 shown , ), , These are respectively applied to the control terminals of the second transistor M2 and the third transistor M3.

[0065] When the external input signal is at a logic high level, the control terminal of the first transistor M1 in the pull-down drive circuit 12 senses the high level and turns on. At this time, the pull-down path is on, the pull-up path is off, and the system draws current outward. The modulated current flowing through the output node is... Conversely, when the external input signal rapidly flips to a logic low level, the control terminal of the fourth transistor M4 in the pull-up drive circuit 11 is turned on. At this time, the pull-up path is on, the pull-down path is off, and the system outputs current. The modulated current flowing through the output node flips to... .

[0066] During the continuous high-frequency switching process, the push-pull drive module 10 ensures that regardless of the state of the input signal, one side of the pull-up drive circuit 11 and the pull-down drive circuit 12 is always on, so that the modulation current generated by the push-pull drive circuit is used to drive the optoelectronic load 30, which greatly saves the static power consumption of the virtual load.

[0067] After the push-pull drive module 10 modulates the alternating drive current, the drive current then flows into the Cherry-Hopper structure, which is composed of the fifth transistor M5, the sixth transistor M6 and the feedback resistor RF, i.e., the transconductance feedback module 20 of this application.

[0068] In traditional architectures, the output of a push-pull current-mode push-pull driver is directly connected to the bias circuit and the opto-load 30, such as Figure 3 (b) It can be seen that the parasitic capacitance that causes the push-pull mechanism to itself ( ) and the parasitic capacitance of the photoelectric load 30 ( These are directly superimposed on the same node, forming superimposed low-frequency dominant poles. In the operation of this application, the current of the push-pull drive module 10 is injected into the control terminals of the fifth transistor M5 and the sixth transistor M6, causing the system to dynamically increase the parasitic capacitance of the push-pull drive module 10 itself (…). The parasitic capacitance of the bias current generation circuit 40 and the optoload 30 is isolated at the input node of the Cherry-Hopper, while the parasitic capacitance of the bias current generation circuit 40 and the optoload 30 is isolated. The output node of the Cherry-Hopper is isolated, thereby splitting the single low-frequency dominant node into two high-frequency poles, which significantly improves the system bandwidth and eye diagram opening.

[0069] As the driving current is continuously injected into the input of the Cherry-Hopper, the injected driving current is converted into a weak control voltage at the input node of the transconductance feedback module 20. After receiving the control voltage, the transconductance unit 21, due to its own transconductance characteristics ( This generates an amplified modulation current at the output of the Cherry-Hopper. Simultaneously, a portion of the modulation current at the output is fed back to the input of the Cherry-Hopper through the feedback resistor RF. After feedback regulation, the equivalent impedance at the Cherry-Hopper input (…) It was suppressed to approximately The equivalent impedance at the output terminal is reduced to approximately .

[0070] This application successfully decomposes the originally low-frequency large pole into two high-frequency small poles located at different frequencies, avoiding the bandwidth bottleneck that limits the transmission of high-frequency signals in the system, so that the system exhibits an extremely flat frequency domain response and the -3dB bandwidth is significantly extended.

[0071] The high-frequency modulated current, amplified by the Cherry-Hopper structure and reshaped with broadband, was then realized. Finally, the opto-load 30, i.e., the vertical-cavity surface-emitting laser (VCSEL), is injected from the output node. The modulation current... Before injection into the VCSEL, the bias current generation circuit 40 stably provides a current of magnitude 40. The DC bias current and the high-frequency alternating modulation current are superimposed at the output node, and the total superimposed current flows into the VCSEL device. Due to the DC bias current... The presence of this ensures that the laser is always biased within an operating range above the threshold current with excellent linearity. Ultimately, the VCSEL device precisely converts the injected high-frequency electrical signal into a high-speed optical signal for outward emission.

[0072] The above description is merely a preferred embodiment of this application and does not limit the patent scope of this application. Any equivalent structural transformations made based on the inventive concept of this application and the contents of the specification and drawings of this application, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this application.

Claims

1. A push-pull drive circuit, characterized by include: The push-pull driver module is used to receive input signals and generate drive current; A transconductance feedback module, electrically connected to the push-pull drive module, includes: A transconducting unit, the input of which is electrically connected to the output of the push-pull drive module, and the output of which is used to connect to an optoelectronic load; The feedback unit has a first terminal electrically connected to the output terminal of the transconductance unit and a second terminal electrically connected to the input terminal of the transconductance unit. The transconductance unit and the feedback unit are connected in parallel to isolate the parasitic capacitance of the push-pull drive module from the parasitic capacitance of the optoelectronic load.

2. The push-pull driver circuit of claim 1, wherein, The push-pull drive module includes: A pull-up drive circuit, the control terminal of which is used to receive the input signal, and the first terminal of which is used to connect to a power supply; A pull-down drive circuit, whose control terminal is used to receive the input signal, whose first terminal is grounded and whose second terminal is electrically connected to the second terminal of the pull-up drive circuit; The common contact of the pull-up drive circuit and the pull-down drive circuit is also electrically connected to the input terminal of the transconductance feedback module to output the drive current to the transconductance feedback module.

3. The push-pull driver circuit of claim 2, wherein, The pull-down drive circuit includes: The first transistor has its first terminal grounded; The second transistor has its first terminal electrically connected to the second terminal of the first transistor, and its second terminal electrically connected to the input terminal of the transconductance feedback module. The pull-up drive circuit includes a third transistor and a fourth transistor; The third transistor has its first terminal electrically connected to the second terminal of the fourth transistor, and its second terminal electrically connected to the second terminal of the second transistor. The first terminal of the fourth transistor is connected to a power source. The input signal is connected to the control terminal of the first transistor or the control terminal of the second transistor; the input signal is connected to the control terminal of the third transistor or the control terminal of the fourth transistor.

4. The push-pull driver circuit of claim 3, wherein, Both the control terminal of the first transistor and the control terminal of the fourth transistor are used to receive the input signal; Both the control terminal of the second transistor and the control terminal of the third transistor are used to receive bias voltage.

5. The push-pull drive circuit according to any one of claims 1 to 4, characterized in that The transconductance unit includes at least one transconductance transistor; The control terminal of the transconductance transistor serves as the input terminal of the transconductance unit, used to receive the drive current output by the push-pull drive module, and generate a control voltage based on the drive current. The controlled terminal of the transconductance transistor serves as the output terminal of the transconductance unit, and is used to output a modulated current to the opto-load according to the control voltage.

6. The push-pull driver circuit of claim 5, wherein, The transconducting unit includes: The fifth transistor has its first terminal grounded; The sixth transistor has its first terminal connected to a power source and its second terminal electrically connected to the second terminal of the fifth transistor to form the output terminal of the transconductance unit. The control terminals of the fifth transistor and the sixth transistor are connected together to form the input terminal of the transconductance unit.

7. The push-pull drive circuit according to any one of claims 1 to 4, characterized in that The feedback unit is a feedback resistor; The feedback resistor is connected between the input and output terminals of the transconductance unit to reduce the equivalent input impedance and equivalent output impedance of the transconductance feedback module.

8. The push-pull driver circuit of claim 7, wherein, The resistance value of the feedback resistor is matched with the transconductance value of the transconductance unit, so that the equivalent input impedance and equivalent output impedance of the transconductance feedback module are both less than the output equivalent resistance of the push-pull drive module.

9. The push-pull drive circuit according to any one of claims 1 to 4, characterized in that It also includes a bias current generation circuit, the output of which is electrically connected to the output of the transconductance feedback module, for providing DC bias current to the optoelectronic load.

10. An optical communication device, comprising: include: Vertical cavity surface-emitting laser; The push-pull drive circuit as described in any one of claims 1 to 9; The push-pull drive circuit is used to provide modulation current for the vertical cavity surface-emitting laser.

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