Trans-impedance amplifier insensitive to high light intensity

Abstract

The invention discloses a transimpedance amplifier insensitive to high light intensity, which comprises an input signal amplification structure and a double-end output structure which are connected with each other, the double-end output structure is also connected with a current bias structure, and the current bias structure is used for providing stable bias current irrelevant to a triode amplification coefficient for the input signal amplification structure. And under the condition that no signal is input, the output reference voltage is equal to the output voltage, and the input signal amplification structure is used for providing a corresponding amplification factor for a wide-range input signal. According to the transimpedance amplifier insensitive to high light intensity, under the condition that the light intensity is large, the triodes enter a saturation region, the output voltage is divided by the resistors and clamped at the lowest output voltage, and the output voltage is prevented from being lower than the common-mode input range of a post-amplifier; when the input optical signal disappears, that is, the output signal is strained to be a high level, the level jump speed is improved through the rapid discharge path.

Description

Technical Field

[0001] The invention belongs to the field of optical fiber receivers, and in particular relates to a transimpedance amplifier that is insensitive to high light intensity. Background Art

[0002] In a fiber optic receiver circuit, the first stage is often a TIA (transimpedance amplifier). The photodiode generates a photocurrent that flows into or out of the TIA module. The TIA then converts the current signal into a voltage signal for output. To ensure the TIA's proper operation and minimize pulse width errors, the input photocurrent is typically limited to a certain range. This can cause the TIA to malfunction over short transmission distances or with high input light intensities. Summary of the Invention

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

[0004] In order to achieve the above-mentioned object of the invention, 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 two-terminal output structure connected to each other, wherein the two-terminal output structure is further connected to a current bias structure; Among them, the current bias structure is used to provide a stable and triode amplification factor for the input signal amplification structure. The bias current Iphoto is irrelevant and ensures that the output reference voltage Vref is equal to the output voltage Vo when there is no signal input. The input signal amplification structure is used to provide corresponding amplification factors for a wide range of input signals. The input signal amplification structure includes a resistor R1, a resistor R2, a resistor R5, a resistor R7, a diode D1, a diode D3 and a transistor Q1; One end of resistor R1 is respectively connected to a 5V power supply and a first connection end of the two-terminal output structure. The other end of resistor R1 is respectively connected to the anode of diode D3 and one end of resistor R2, and serves as an output end for outputting a reference voltage Vref. The other end of resistor R2 is respectively connected to the cathode of diode D1, one end of resistor R5, and the collector of transistor Q1. The base of transistor Q1 is respectively 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 respectively connected to the other end of resistor R7 and the second connection end of the two-terminal output structure.

[0005] Furthermore: the two-terminal output structure includes a resistor R3, a resistor R4, a resistor R6, a resistor R8, a resistor Rf, a diode D2, a diode D4 and a transistor Q2; Among them, one end of the resistor R3 serves as the first connection end of the two-terminal output structure, the other end of the resistor R3 is respectively connected to one end of the resistor R4 and the anode of the diode D4, and serves as the output end of the output voltage Vo, the other end of the resistor R4 is respectively connected to the cathode of the diode D2, one end of the resistor R6, and the collector of the transistor Q2, the base of the transistor Q2 is respectively connected to one end of the resistor R8, one end of the resistor Rf, the anode of the diode D2, and the other end of the resistor R6, and serves as the third connection end of the two-terminal output structure, the other end of the resistor R8 serves as the second connection end of the two-terminal output structure, the emitter of the transistor Q2 is grounded, and the other end of the resistor Rf is connected to the cathode of the diode D4.

[0006] The beneficial effect of the above further solution is that the output of the input signal amplification structure and the two-terminal 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.

[0007] Furthermore: the current bias structure includes a resistor R9, a resistor R10, a resistor R11, a grounding resistor R12, a diode D5 and a transistor Q3; Among them, one end of the resistor R9 is respectively connected to the third connection terminal of the two-terminal output structure, one end of the resistor R11 and the anode of the diode D5, the cathode of the diode D5 is respectively connected to the grounding resistor R12 and one end of the resistor R10, the other end of the resistor R11 is connected to a 5V power supply, the other end of the resistor R9 is connected to the collector of the transistor Q3, the base of the transistor Q3 is connected to the other end of the resistor R10, and the emitter of the transistor Q3 is grounded.

[0008] Furthermore, the transistor Q1 and the transistor Q2 are bipolar transistors, so that the bias current Iphoto passing through the third connection terminal of the two-terminal output structure is directly input into the base of the transistor Q1 and the transistor Q2.

[0009] The beneficial effect of the above further solution is that the resistors R5 and R6 between the collector and base of the transistors Q1 and Q2 are connected in reverse parallel with the 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.

[0010] Furthermore, the resistance ratio of the resistor R7 and the resistor R8 is determined according to the common mode range of the post-stage amplifier so that the minimum output voltage is within the common mode range.

[0011] The beneficial effects of the present invention are: (1) The present invention provides a transimpedance amplifier that is insensitive to high light intensity. Under normal light intensity conditions, the transistor operates in the amplification region and can be used as a normal transimpedance amplifier. Under high light intensity conditions, the transistor enters the saturation region, and the output voltage is clamped to the minimum output voltage by the resistor divider to prevent the output voltage from falling below the common-mode input range of the subsequent amplifier. When the input light signal disappears, that is, the output signal should become a high level, the level jump speed is improved through the fast discharge path.

[0012] (2) Due to the symmetry of the input signal amplification structure and the two-terminal output structure of the transimpedance amplifier insensitive to high light intensity proposed by the present 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.

[0013] (3) The present invention has the outstanding advantages of reliable performance and small chip area. It can achieve the clamping of output current and voltage without the need for a complex structure amplifier and without increasing delay. It has good use effect in some situations where a small chip area and high light intensity are required. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic diagram of a transimpedance amplifier that is insensitive to high light intensity according to the present invention. DETAILED DESCRIPTION

[0015] The specific embodiments of the present invention are described below to facilitate understanding of the present invention by those skilled in the art. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the appended claims, these changes are obvious, and all inventions and creations utilizing the concepts of the present invention are protected.

[0016] 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 two-terminal output structure connected to each other, and the two-terminal output structure is also connected to a current bias structure; Among them, the current bias structure is used to provide a stable and triode amplification factor for the input signal amplification structure. The bias current Iphoto is irrelevant and ensures that the output reference voltage Vref is equal to the output voltage Vo when there is no signal input. The input signal amplification structure is used to provide corresponding amplification factors for a wide range of input signals. The input signal amplification structure includes a resistor R1, a resistor R2, a resistor R5, a resistor R7, a diode D1, a diode D3 and a transistor Q1; One end of resistor R1 is respectively connected to a 5V power supply and a first connection end of the two-terminal output structure. The other end of resistor R1 is respectively connected to the anode of diode D3 and one end of resistor R2, and serves as an output end for outputting a reference voltage Vref. The other end of resistor R2 is respectively connected to the cathode of diode D1, one end of resistor R5, and the collector of transistor Q1. The base of transistor Q1 is respectively 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 respectively connected to the other end of resistor R7 and the second connection end of the two-terminal output structure.

[0017] The double-terminal output structure includes resistor R3, resistor R4, resistor R6, resistor R8, resistor Rf, diode D2, diode D4 and transistor Q2; Among them, one end of the resistor R3 serves as the first connection end of the two-terminal output structure, the other end of the resistor R3 is respectively connected to one end of the resistor R4 and the anode of the diode D4, and serves as the output end of the output voltage Vo, the other end of the resistor R4 is respectively connected to the cathode of the diode D2, one end of the resistor R6, and the collector of the transistor Q2, the base of the transistor Q2 is respectively connected to one end of the resistor R8, one end of the resistor Rf, the anode of the diode D2, and the other end of the resistor R6, and serves as the third connection end of the two-terminal output structure, the other end of the resistor R8 serves as the second connection end of the two-terminal output structure, the emitter of the transistor Q2 is grounded, and the other end of the resistor Rf is connected to the cathode of the diode D4.

[0018] like Figure 1 As shown, in this embodiment, the output of the input signal amplification structure and the dual-terminal 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.

[0019] In transistors Q1 and Q2, resistors R5 and R6 between the collector and base are connected in anti-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 quickly discharged.

[0020] The current bias structure includes a resistor R9, a resistor R10, a resistor R11, a grounding resistor R12, a diode D5 and a transistor Q3; Among them, one end of the resistor R9 is respectively connected to the third connection terminal of the two-terminal output structure, one end of the resistor R11 and the anode of the diode D5, the cathode of the diode D5 is respectively connected to the grounding resistor R12 and one end of the resistor R10, the other end of the resistor R11 is connected to a 5V power supply, the other end of the resistor R9 is connected to the collector of the transistor Q3, the base of the transistor Q3 is connected to the other end of the resistor R10, and the emitter of the transistor Q3 is grounded.

[0021] The transistor Q1 and the transistor Q2 are bipolar transistors, so that the bias current Iphoto passing through the third connection terminal of the two-terminal output structure is directly input into the base of the transistor Q1 and the transistor Q2.

[0022] The resistance ratio of the resistor R7 and the resistor R8 is determined according to the common mode range of the post-stage amplifier so that the minimum output voltage is within the common mode range.

[0023] The working process of a transimpedance amplifier insensitive to high light intensity of the present invention is as follows: In a specific working process, the reverse bias voltage of the photodiode of the front stage can be generated by another structure that is the same as the bias current structure, and the common mode input range of the amplifier of the rear stage is 900mV to 2V.

[0024] Because the photodiode bias circuit draws a relatively large current when the photocurrent is high, the collector current of the photodiode bias circuit should be appropriately increased based on the actual application conditions. Since the common-mode input range of the subsequent amplifier is a minimum of 900mV, the ratio of resistors R1 to R2, and R3 to R4, should be set to 4:1 for a 5V power supply.

[0025] When there is no current input, transistors Q1 and Q2 work in the amplification region, and diode D3 is forward biased. Due to the negative feedback effect, a path can be obtained. It has nothing to do with the collector current, which is less affected by temperature. Since the resistors R7 and R8 are equal and the resistor Rf is larger, the transistor Q2 is also under the same bias conditions, so the output reference voltage Vref and the output voltage Vo are equal at this time.

[0026] When the input current signal is small, transistors Q1 and Q2 still work in the amplification area. At this time, the transresistance amplification factor is:

[0027] Deep negative feedback is required, 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 post-amplifier output, and the output reference voltage is consistent with that when there is no photocurrent input.

[0028] When the input current signal is large, transistor Q2 quickly enters the saturation region. At this time, the output voltage is determined by the resistance divider of 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 the ground through the fast discharge path, so that the transimpedance amplifier can quickly return to the amplification region and operate normally.

[0029] The beneficial effects of the present invention are as follows: the present invention provides a transimpedance amplifier that is insensitive to high light intensity; under normal light intensity conditions, the transistor operates in the amplification region and can be used as a normal transimpedance amplifier; under high light intensity conditions, the transistor enters the saturation region, and the output voltage is clamped to the minimum 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, that is, when the output signal should become a high level, the level jump speed is improved through a fast discharge path.

[0030] Due to the symmetry of the input signal amplification structure and the double-ended output structure of the transimpedance amplifier insensitive to high light intensity of the present invention, the output voltage Vo and the output reference voltage Vref have equal common-mode levels, so that the transimpedance amplifier directly outputs a pair of differential signals.

[0031] The present invention has the outstanding advantages of reliable performance and small chip area occupation.

[0032] In the description of the present invention, it should be understood that the terms "center", "thickness", "upper", "lower", "horizontal", "top", "bottom", "inner", "outer", "radial", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying the relative importance or the number of technical features implicitly specified. Therefore, the features defined by "first", "second", and "third" may explicitly or implicitly include one or more of such features.

Claims

1. A transimpedance amplifier insensitive to high light intensity, characterized in that: It includes an input signal amplification structure and a two-terminal output structure connected to each other, and the two-terminal output structure is also connected to a current bias structure; Among them, the current bias structure is used to provide a stable and triode amplification factor for the input signal amplification structure. The bias current Iphoto is irrelevant and ensures that the output reference voltage Vref is equal to the output voltage Vo when there is no signal input. The input signal amplification structure is used to provide corresponding amplification factors for a wide range of input signals. The input signal amplification structure includes a resistor R1, a resistor R2, a resistor R5, a resistor R7, a diode D1, a diode D3 and a transistor Q1; One end of resistor R1 is respectively connected to a 5V power supply and a first connection end of the two-terminal output structure. The other end of resistor R1 is respectively connected to the anode of diode D3 and one end of resistor R2, and serves as an output end for outputting a reference voltage Vref. The other end of resistor R2 is respectively connected to the cathode of diode D1, one end of resistor R5, and the collector of transistor Q1. The base of transistor Q1 is respectively 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 respectively connected to the other end of resistor R7 and the second connection end of the two-terminal output structure.

2. The transimpedance amplifier insensitive to high light intensity according to claim 1, characterized in that: The double-terminal output structure includes resistor R3, resistor R4, resistor R6, resistor R8, resistor Rf, diode D2, diode D4 and transistor Q2; Among them, one end of the resistor R3 serves as the first connection end of the two-terminal output structure, the other end of the resistor R3 is respectively connected to one end of the resistor R4 and the anode of the diode D4, and serves as the output end of the output voltage Vo, the other end of the resistor R4 is respectively connected to the cathode of the diode D2, one end of the resistor R6, and the collector of the transistor Q2, the base of the transistor Q2 is respectively connected to one end of the resistor R8, one end of the resistor Rf, the anode of the diode D2, and the other end of the resistor R6, and serves as the third connection end of the two-terminal output structure, the other end of the resistor R8 serves as the second connection end of the two-terminal output structure, the emitter of the transistor Q2 is grounded, and the other end of the resistor Rf is connected to the cathode of the diode D4.

3. The transimpedance amplifier insensitive to high light intensity according to claim 2, characterized in that: The current bias structure includes a resistor R9, a resistor R10, a resistor R11, a grounding resistor R12, a diode D5 and a transistor Q3; Among them, one end of the resistor R9 is respectively connected to the third connection terminal of the two-terminal output structure, one end of the resistor R11 and the anode of the diode D5, the cathode of the diode D5 is respectively connected to the grounding resistor R12 and one end of the resistor R10, the other end of the resistor R11 is connected to a 5V power supply, the other end of the resistor R9 is connected to the collector of the transistor Q3, the base of the transistor Q3 is connected to the other end of the resistor R10, and the emitter of the transistor Q3 is grounded.

4. The transimpedance amplifier insensitive to high light intensity according to claim 2, characterized in that: The transistor Q1 and the transistor Q2 are bipolar transistors, so that the bias current Iphoto passing through the third connection terminal of the two-terminal output structure is directly input into the base of the transistor Q1 and the transistor Q2.

5. The transimpedance amplifier insensitive to high light intensity according to claim 2, characterized in that: The resistance ratio of the resistor R7 and the resistor R8 is determined according to the common mode range of the post-stage amplifier so that the minimum output voltage is within the common mode range.

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