A transimpedance amplifier that is insensitive to high light intensity

Abstract

This invention discloses a transimpedance amplifier insensitive to high light intensity, comprising an interconnected input signal amplification structure and a dual-ended output structure. The dual-ended output structure is also connected to a current bias structure. The current bias structure provides a stable bias current to the input signal amplification structure, independent of the transistor's amplification factor, and ensures that the output reference voltage and output voltage are equal when there is no signal input. The input signal amplification structure provides a corresponding amplification factor for a wide range of input signals. This invention provides a transimpedance amplifier insensitive to high light intensity. Under high light intensity, the transistor enters the saturation region, and the output voltage is clamped to the lowest output voltage by a resistor divider, preventing the output voltage from falling below the common-mode input range of the subsequent amplifier. When the input light signal disappears, i.e., when the output signal should return to a high level, a fast discharge path improves the level transition speed.

Description

Technical Field

[0001] This invention belongs to the field of fiber optic receivers, and specifically relates to a transimpedance amplifier that is insensitive to high light intensity. Background Technology

[0002] In fiber optic receiver circuits, the first stage is often a TIA (transimpedance amplifier). A photodiode generates photocurrent that flows into or out of the TIA module. The TIA then converts the current signal into a voltage signal for output. Usually, in order for the TIA to work properly and for the pulse width error to be small enough, the input photocurrent is limited to a certain range. This can cause the TIA to malfunction when the transmission distance is short or the input light intensity is strong. Summary of the Invention

[0003] In view of the above-mentioned shortcomings in the prior art, the present invention provides a transimpedance amplifier that is insensitive to high light intensity, which solves the problem that transimpedance amplifiers that are insensitive to high light intensity cannot work properly under high light intensity conditions.

[0004] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is as follows: a transimpedance amplifier that is insensitive to high light intensity, comprising an input signal amplification structure and a dual-ended output structure connected to each other, wherein the dual-ended output structure is also connected to a current biasing structure.

[0005] The current bias structure is used to provide a stable current bias for the input signal amplification structure, which is consistent with the amplification factor of the transistor. The bias current Iphoto is independent, and the output reference voltage Vref and output voltage Vo are equal when there is no signal input. The input signal amplification structure is used to provide the corresponding amplification factor for a wide range of input signals.

[0006] The input signal amplification structure includes resistors R1, R2, R5, and R7, diodes D1 and D3, and transistor Q1;

[0007] One end of resistor R1 is connected to the 5V power supply and the first connection terminal of the dual-ended output structure. The other end of resistor R1 is connected to the anode of diode D3 and one end of resistor R2, and serves as the output terminal of the output reference voltage Vref. The other end of resistor R2 is connected to the cathode of diode D1, one end of resistor R5, and the collector of transistor Q1. The base of transistor Q1 is connected to the anode of diode D1, the other end of resistor R5, and one end of resistor R7. The emitter of transistor Q1 is grounded. The anode of diode D1 is connected to the other end of resistor R7 and the second connection terminal of the dual-ended output structure.

[0008] Furthermore: the dual-ended output structure includes resistors R3, R4, R6, R8, Rf, diode D2, diode D4, and transistor Q2;

[0009] In this configuration, one end of resistor R3 serves as the first connection terminal of the dual-ended output structure. The other end of resistor R3 is connected to one end of resistor R4 and the positive terminal of diode D4, serving as the output terminal of output voltage Vo. The other end of resistor R4 is connected to the negative terminal of diode D2, one end of resistor R6, and the collector of transistor Q2. The base of transistor Q2 is connected to one end of resistor R8, one end of resistor Rf, the positive terminal of diode D2, and the other end of resistor R6, serving as the third connection terminal of the dual-ended output structure. The other end of resistor R8 serves as the second connection terminal of the dual-ended output structure. The emitter of transistor Q2 is grounded, and the other end of resistor Rf is connected to the negative terminal of diode D4.

[0010] The beneficial effect of the above-mentioned further scheme is that the output of the input signal amplification structure and the dual-ended output structure is between the two resistors of the transistor collector, so that the output voltage will not be approximately grounded due to the transistor entering the saturation region.

[0011] Furthermore: the current bias structure includes resistors R9, R10, R11, grounding resistor R12, diode D5, and transistor Q3;

[0012] In this configuration, one end of resistor R9 is connected to the third connection terminal of the dual-ended output structure, one end of resistor R11, and the positive terminal of diode D5. The negative terminal of diode D5 is connected to the grounding resistor R12 and one end of resistor R10. The other end of resistor R11 is connected to the 5V power supply. The other end of resistor R9 is connected to the collector of transistor Q3. The base of transistor Q3 is connected to the other end of resistor R10. The emitter of transistor Q3 is grounded.

[0013] Furthermore, transistors Q1 and Q2 are bipolar transistors, so that the bias current Iphoto through the third connection terminal of the dual-ended output structure is directly input to the base of transistors Q1 and Q2.

[0014] The beneficial effect of the above-mentioned further scheme is that the resistors R5 and R6 between the collector and base of transistors Q1 and Q2 are connected in reverse parallel with Schottky diodes D1 and D2 to form a fast discharge path, so that the parasitic capacitance of the photodiode and the excess stored charge of the bipolar transistor can be discharged quickly.

[0015] Furthermore, the resistance ratio of resistors R7 and R8 is determined based on the common-mode range of the subsequent amplifier to ensure that the minimum output voltage is within the common-mode range.

[0016] The beneficial effects of this invention are as follows:

[0017] (1) This invention provides a transimpedance amplifier that is not sensitive to high light intensity. Under normal light intensity, the transistor operates in the amplification region and can be used as a normal transimpedance amplifier. Under high light intensity, the transistor enters the saturation region, and the output voltage is clamped to the lowest output voltage by the resistor voltage divider to prevent the output voltage from being lower than the common-mode input range of the subsequent amplifier. When the input light signal disappears, that is, when the output signal should be high level, the level transition speed is improved by the fast discharge path.

[0018] (2) Due to the symmetry of the input signal amplification structure and the dual-ended output structure of the transimpedance amplifier that is insensitive to high light intensity proposed in this invention, the common-mode levels of the output voltage Vo and the output reference voltage Vref are equal, so that the transimpedance amplifier directly outputs a pair of differential signals.

[0019] (3) The present invention has the outstanding advantages of reliable performance and small chip area. It can clamp the output current and voltage without the need for complex structure amplifiers and without increasing the delay. It has good performance in some cases where the chip area is required to be small and the light intensity is strong. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a transimpedance amplifier that is insensitive to high light intensity according to the present invention. Detailed Implementation

[0021] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0022] like Figure 1 As shown, in one embodiment of the present invention, a transimpedance amplifier that is insensitive to high light intensity includes an input signal amplification structure and a dual-ended output structure connected to each other, and the dual-ended output structure is also connected to a current biasing structure.

[0023] The current bias structure is used to provide a stable current bias for the input signal amplification structure, which is consistent with the amplification factor of the transistor. The bias current Iphoto is independent, and the output reference voltage Vref and output voltage Vo are equal when there is no signal input. The input signal amplification structure is used to provide the corresponding amplification factor for a wide range of input signals.

[0024] The input signal amplification structure includes resistors R1, R2, R5, and R7, diodes D1 and D3, and transistor Q1;

[0025] One end of resistor R1 is connected to the 5V power supply and the first connection terminal of the dual-ended output structure. The other end of resistor R1 is connected to the anode of diode D3 and one end of resistor R2, and serves as the output terminal of the output reference voltage Vref. The other end of resistor R2 is connected to the cathode of diode D1, one end of resistor R5, and the collector of transistor Q1. The base of transistor Q1 is connected to the anode of diode D1, the other end of resistor R5, and one end of resistor R7. The emitter of transistor Q1 is grounded. The anode of diode D1 is connected to the other end of resistor R7 and the second connection terminal of the dual-ended output structure.

[0026] The dual-ended output structure includes resistors R3, R4, R6, R8, and Rf, diodes D2 and D4, and transistor Q2;

[0027] In this configuration, one end of resistor R3 serves as the first connection terminal of the dual-ended output structure. The other end of resistor R3 is connected to one end of resistor R4 and the positive terminal of diode D4, serving as the output terminal of output voltage Vo. The other end of resistor R4 is connected to the negative terminal of diode D2, one end of resistor R6, and the collector of transistor Q2. The base of transistor Q2 is connected to one end of resistor R8, one end of resistor Rf, the positive terminal of diode D2, and the other end of resistor R6, serving as the third connection terminal of the dual-ended output structure. The other end of resistor R8 serves as the second connection terminal of the dual-ended output structure. The emitter of transistor Q2 is grounded, and the other end of resistor Rf is connected to the negative terminal of diode D4.

[0028] like Figure 1 As shown, in this embodiment, the output of the input signal amplification structure and the dual-ended output structure is between the two resistors of the transistor collector, so that the output voltage will not be approximately grounded due to the transistor entering the saturation region.

[0029] In transistors Q1 and Q2, resistors R5 and R6 between the collector and base are connected in reverse parallel with Schottky diodes D1 and D2 to form a fast discharge path, so that the parasitic capacitance of the photodiode and the excess stored charge of the bipolar transistor can be discharged quickly.

[0030] The current bias structure includes resistors R9, R10, R11, grounding resistor R12, diode D5, and transistor Q3;

[0031] In this configuration, one end of resistor R9 is connected to the third connection terminal of the dual-ended output structure, one end of resistor R11, and the positive terminal of diode D5. The negative terminal of diode D5 is connected to the grounding resistor R12 and one end of resistor R10. The other end of resistor R11 is connected to the 5V power supply. The other end of resistor R9 is connected to the collector of transistor Q3. The base of transistor Q3 is connected to the other end of resistor R10. The emitter of transistor Q3 is grounded.

[0032] Transistors Q1 and Q2 are bipolar transistors, allowing the bias current Iphoto from the third terminal of the dual-ended output structure to be directly input to the base of transistors Q1 and Q2.

[0033] The ratio of the resistance values ​​of resistors R7 and R8 is determined based on the common-mode range of the subsequent amplifier to ensure that the minimum output voltage is within the common-mode range.

[0034] The operation process of a transimpedance amplifier that is insensitive to high light intensity according to the present invention is as follows:

[0035] In a specific operating process, the reverse bias voltage of the photodiode in the front stage can be generated by another structure with the same bias current structure, and the common-mode input range of the amplifier in the back stage is 900mV to 2V.

[0036] Because a relatively large portion of the current is drawn away from the photodiode bias circuit when the photocurrent is high, the collector current of the photodiode bias circuit should be appropriately increased according to the actual application conditions. Since the minimum common-mode input range of the subsequent amplifier is 900mV, the ratio of resistors R1 and R2, and resistors R3 and R4, should be set to 4:1 under a 5V power supply voltage.

[0037] When there is no current input, transistors Q1 and Q2 operate in the amplification region, and diode D3 is forward biased. Due to the negative feedback, a current path can be obtained. The collector current, which is less affected by temperature, is irrelevant. Since resistors R7 and R8 are equal and resistor Rf is larger, and transistor Q2 is also under the same bias conditions, the output reference voltage Vref and the output voltage Vo are equal at this time.

[0038] When the input current signal is small, transistors Q1 and Q2 still operate in the amplification region. The transimpedance amplification factor at this time is:

[0039]

[0040] The requirement is to satisfy deep negative feedback, that is, R4+R3 and Rf are roughly on the same order of magnitude, the output voltage is within the common-mode range of the output of the subsequent amplifier, and the output reference voltage is consistent with that when there is no photocurrent input.

[0041] When the input current signal is large, transistor Q2 quickly enters the saturation region. At this time, the output voltage is determined by the voltage division of resistors R3 and R4. When the signal disappears, the excess stored charge of transistor Q2 and the parasitic capacitance of the photodiode will be discharged to ground through the fast discharge path, so that the transimpedance amplifier can quickly return to the amplification region and work normally.

[0042] The beneficial effects of this invention are as follows: This invention provides a transimpedance amplifier that is insensitive to high light intensity. Under normal light intensity, the transistor operates in the amplification region and can be used as a normal transimpedance amplifier. Under high light intensity, the transistor enters the saturation region, and the output voltage is clamped to the lowest output voltage by the resistor voltage divider, preventing the output voltage from falling below the common-mode input range of the subsequent amplifier. When the input light signal disappears, that is, when the output signal should be at a high level, the level transition speed is improved through a fast discharge path.

[0043] Due to the symmetry of the input signal amplification structure and the dual-ended output structure of the transimpedance amplifier that is insensitive to high light intensity, the common-mode levels of the output voltage Vo and the output reference voltage Vref are equal, enabling the transimpedance amplifier to directly output a pair of differential signals.

[0044] This invention has the outstanding advantages of reliable performance and small chip area.

[0045] In the description of this invention, it should be understood that the terms "center," "thickness," "upper," "lower," "horizontal," "top," "bottom," "inner," "outer," and "radial," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying the relative importance or the number of technical features implicitly specified. Therefore, a feature defined by "first," "second," and "third" may explicitly or implicitly include one or more of that feature.

Claims

1. A transimpedance amplifier that is insensitive to high light intensity, characterized in that, It includes an interconnected input signal amplification structure and a dual-ended output structure, and the dual-ended output structure is also connected to a current bias structure. The current bias structure is used to provide a stable current bias for the input signal amplification structure, which is consistent with the amplification factor of the transistor. The bias current Iphoto is independent, and the output reference voltage Vref and output voltage Vo are equal when there is no signal input. The input signal amplification structure is used to provide the corresponding amplification factor for a wide range of input signals. The input signal amplification structure includes resistors R1, R2, R5, and R7, diodes D1 and D3, and transistor Q1; One end of resistor R1 is connected to the 5V power supply and the first connection terminal of the dual-ended output structure. The other end of resistor R1 is connected to the anode of diode D3 and one end of resistor R2, and serves as the output terminal of the output reference voltage Vref. The other end of resistor R2 is connected to the cathode of diode D1, one end of resistor R5, and the collector of transistor Q1. The base of transistor Q1 is connected to the anode of diode D1, the other end of resistor R5, and one end of resistor R7. The emitter of transistor Q1 is grounded. The anode of diode D1 is connected to the other end of resistor R7 and the second connection terminal of the dual-ended output structure. The dual-ended output structure includes resistors R3, R4, R6, R8, and Rf, diodes D2 and D4, and transistor Q2; In this configuration, one end of resistor R3 serves as the first connection terminal of the dual-ended output structure. The other end of resistor R3 is connected to one end of resistor R4 and the positive terminal of diode D4, serving as the output terminal of output voltage Vo. The other end of resistor R4 is connected to the negative terminal of diode D2, one end of resistor R6, and the collector of transistor Q2. The base of transistor Q2 is connected to one end of resistor R8, one end of resistor Rf, the positive terminal of diode D2, and the other end of resistor R6, serving as the third connection terminal of the dual-ended output structure. The other end of resistor R8 serves as the second connection terminal of the dual-ended output structure. The emitter of transistor Q2 is grounded, and the other end of resistor Rf is connected to the negative terminal of diode D4.

2. The transimpedance amplifier insensitive to high light intensity according to claim 1, characterized in that, The current bias structure includes resistors R9, R10, R11, grounding resistor R12, diode D5, and transistor Q3; In this configuration, one end of resistor R9 is connected to the third connection terminal of the dual-ended output structure, one end of resistor R11, and the positive terminal of diode D5. The negative terminal of diode D5 is connected to the grounding resistor R12 and one end of resistor R10. The other end of resistor R11 is connected to the 5V power supply. The other end of resistor R9 is connected to the collector of transistor Q3. The base of transistor Q3 is connected to the other end of resistor R10. The emitter of transistor Q3 is grounded.

3. The transimpedance amplifier insensitive to high light intensity according to claim 1, characterized in that, Transistors Q1 and Q2 are bipolar transistors, allowing the bias current Iphoto from the third terminal of the dual-ended output structure to be directly input to the base of transistors Q1 and Q2.

4. The transimpedance amplifier insensitive to high light intensity according to claim 1, characterized in that, The ratio of the resistance values ​​of resistors R7 and R8 is determined based on the common-mode range of the subsequent amplifier to ensure that the minimum output voltage is within the common-mode range.

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