TWI235546B - Improved transimpedance amplifier circuit - Google Patents

Abstract

The present invention relates to an improved transimpedance amplifier circuit, comprising a bipolar transistor differential amplifier having an input end connected to a photo diode and another input end connected to a reference voltage, and a feedback circuit , which is a resistor-and-capacitor-parallel-connected circuit, comprising a capacitor and a resistor connected to each other in parallel, which are serially connected to a complementary metal-oxide-semiconductor field effect transistor. The resistor-and-capacitor-parallel-connected circuit has one end connected to the input end of the bipolar transistor differential amplifier and another end connected to an output of the bipolar transistor differential amplifier. By such an arrangement it combines bipolar transistor and complementary metal-oxide-semiconductor field effect transistor to realize the purpose of high response, low noise and low power consumption.

Description

1235546 Nine, · _ said _: Discussion [Technical field to which the invention belongs] The present invention relates to an improved circuit for a transimpedance amplifier, and in particular, to an improved circuit for a transimpedance amplifier capable of achieving high-speed response, low noise, and low power. . [Previous Technology] Optoelectronics has become a communication and data storage medium today. In terms of communication, the use of optical fibers with far better bandwidth than cables, and in the field of data storage, near-field optical discs (capacity up to 100G) have also been introduced. However, regardless of whether light or electronics are used as communication and storage media, they still need to be converted to voltage for further data processing or presentation. Generally, they are based on photodiode volume circuit (ph〇t〇).

Diode Integrated Circuit (PDIC for short). In addition to converting the laser light into a voltage, the PDIC also generates signals such as RF, tracking error, and focus error, and then sends the signal to the next-stage preamplifier for processing in order to return the signal and Complete the lock and focus. Therefore, although PDIC is a small circuit, it plays a very important role. The pdic contains two parts, one is a photodiode sensor, which converts the reflected laser light source into a current (electron flow), and the other is an integrated circuit. This circuit The function is to convert the current into a voltage signal and provide gain for use by the preamp of the next stage. This is because the voltage signal from the transimpedance amplifier does not have large amplitude, so it is often necessary to connect another preamp to amplify the voltage signal. The integrated circuit part is a transimpedance amplifier (Transimpedance Ampifier, referred to as TIA). Its function is to convert the current signal into a voltage signal. There are many ways to design it, depending on the process and specifications. The architecture of the transimpedance amplifier circuit can be open-loop or closed-loop. If an open-loop 1235546 structure is used to design a transimpedance amplifier, the noise generated by the resistor is directly connected to the output, and the lower the electrical waste, the more serious the noise, so it is not practical. Therefore, the transimpedance amplifiers use a closed-loop feedback structure. to realise. Because the input signal is a current, the transimpedance amplifier must have a low input impedance, so the most common and widely used structure of the transimpedance amplifier is the common emitter circuit and feedback structure from the base input. Differential input from the reference voltage, and then amplified by the first-stage voltage, and finally the output of the buffer stage; a few are common base circuit and feedback structure using the emitter input. The transimpedance amplifier uses a shunt-shunt feedback architecture to provide transimpedance gain, which can provide high gain, high frequency bandwidth, and low noise characteristics. As shown in Figure 1, Figure 1 is a schematic diagram of the circuit structure of a transimpedance amplifier. The transimpedance amplifier is composed of an amplifier Amp (gain is _A), a feedback resistance Rfb, and a reference voltage Vref. The transimpedance amplifier can convert the photocurrent lpd generated by the photodiode PD into a voltage vout. Because the empty area of the photodiode has a capacitive effect (so-called parasitic capacitance), a capacitor Cfb is generally used in parallel with the feedback resistor Rfb as compensation to avoid unstable voltage gain, as shown in Figure 2, where: Capacitor Cfb will set an on-off control. A switch SW2 can also be set to control the conduction of the feedback resistor Rfb 'as shown in FIG. As shown in Figure 4, in order to obtain high gain and better bandwidth response at the same time, the general transimpedance amplifier will use a two-stage amplifier circuit structure. The gain of the second amplifier Amp2 is -A2, and the feedback resistance is Rfb2. Cfb2 is used as compensation to control switch 邠 4 of feedback resistor Rfb2 and switch SW3 of control capacitor Wb2. The reference voltage is yref2. The implementation circuit of the transimpedance amplifier can be divided into two types. One is achieved by using a bipolar transistor (Bipolar TransislOr), as shown in Figure 5. Schematic diagram of the circuit of the transimpedance amplifier The switch SW2 in 1235546 is achieved by the bipolar transistor φΐ, and the amplifier Amp is achieved by the two bipolar transistors Q1, Q2, and the current source circuits II, 12, 13. In addition, in order to stabilize the rotation, a buffer amplifier (Buffer) B can be connected to the amplifier output. The other is achieved by using a complementary metal-oxide-semiconductor field effect transistor (CMOS for short), as shown in Figure 6. The switch SW2 in the schematic diagram of the transimpedance amplifier circuit is achieved by a complementary metal-oxide-semiconductor half-field-effect transistor φ2, and the amplifier Amp is composed of two complementary metal-oxide-semiconductor half-field-effect transistors Q3, Q4, and a current source circuit II, 12, 13 To reach. In addition, in order to stabilize the output, a buffer amplifier (Buffer) B may be connected to the output end of the amplifier. The aforementioned two circuit architectures are similar, with only different components being achieved. Bipolar transistors and metal-oxide-semiconductor half-effect transistors are widely used in electronic and communication fields such as switches, signal amplifiers, power amplifiers, and current mirrors. Among them, M0SFET is the most widely used transistor type in various occasions, especially in computer and communication-related electronic equipment. This is because the structure of M0SFET is particularly suitable for being reduced, and the power demand is also small. On the same chip It becomes feasible to make tens of millions of transistor switches. Compared with the two transistors, the metal-oxide-semiconductor half-effect transistor is less able to meet the characteristics requirements of the GHz-level input signal, but the double-carrier transistor has no problems. Therefore, most of the baseband signal processing circuits use metal-oxide semi-effect transistor. In terms of RF / IF signal processing, bipolar transistors are mostly used. In terms of power consumption, metal-oxide-semiconductor half-effect transistors are much smaller than bipolar transistors. Therefore, no matter which one is used, there are Imperfections. 1235546 [Content of the invention] There are still some imperfections in the traditional transimpedance amplifier circuit. After years of continuous research and development, the inventor finally developed this kind of shortcomings that can improve the conventional transimpedance amplifier A || Improved circuit for high-speed response, low noise and low power transimpedance amplifiers. The improved transimpedance amplifier circuit of the present invention uses a double-carrier transistor (i.e., ㈣) combined with advanced complementary metal-oxide-semiconductor field-effect transistor technology (⑽s) to form a double-carrier complementary metal-oxide semiconductor (BiCMOS). The use of complementary metal-oxide-semiconductor half-field-effect transistors as switches achieves better switching circuit characteristics and low power loss', and the use of Weizi transistors as differential switches achieves high-speed and better bandwidth response. That is, the parts in the circuit that need high-speed and high-current drive are made of bipolar transistors. The parts that require high integration and low power consumption are made of complementary metal-oxide-semiconductor half-field effect transistors to provide more High speed, lower noise, and lower power characteristics. The improved circuit of the transimpedance amplifier of the present invention has the advantages of: 1. It has the advantage of low noise in the bipolar transistor 2. It has better switching circuit characteristics by using a complementary metal-oxide-semiconductor field-effect transistor as a switch 3. Avoiding complementary gold The interface capacitance of the oxygen half field effect transistor does not match the interface capacitance of the photodiode and high noise is generated in the high series. In order to check the characteristics of the present invention more easily, please refer to the following drawings and the implementation of the present invention. Ways to explain. 1235546 [Embodiment] Please refer to Figure VII. Figure VII shows an improved circuit diagram of the Japanese resistance amplifier. The improved transimpedance amplifier circuit of the present invention comprises a differential double-carrier transistor amplifier and a feedback circuit. Among them, the bipolar transistor Q5 and Q6 are connected in a common emitter manner. The -input terminal of the differential bipolar transistor amplifier is connected to the photodiode pD. * The other input terminal is connected to the reference diode. The hybrid circuit is a capacitor Cfbl connected in series with the complementary metal-oxide-semiconductor half-field-effect transistor and-a resistor Rfbi connected in series with the complementary metal-oxide-semiconductor half-field-effect transistor switch in parallel to form a phase-feed circuit that is The input terminal of the differential bipolar transistor amplifier, one end is connected to the output terminal VQUt of the differential bipolar transistor amplifier. The output terminal can be connected to a buffer amplifier β at the output voltage as the input of the next stage circuit. The differential bipolar transistor amplifier has three current sources ^ 12,13. There are many kinds of current source implementation circuits. For example, the base of the bipolar transistor can be biased, and a resistor can be connected in series with the emitter. To reach. With such a design, a combination of a two-carrier transistor and a metal-oxide-semiconductor half-field effect transistor is used to achieve high-speed response, low noise, and low power. In order to obtain high gain and better bandwidth response at the same time, the general transimpedance amplifier will use a two-stage amplifier circuit structure, as shown in Figure Eight Lion. The second reduction of the electric scale is as described above, in which the bipolar transistors Q7 and Q8 are connected in a common emitter manner, and one input terminal of the differential bipolar transistor amplifier is connected to the aforementioned front-stage output terminal. While the other end is connected to the reference voltage Vref2; the feedback circuit consists of a capacitor ㈣ connected in series with the complementary metal-oxide-semiconductor half-effect transistor ㈣ and-connected in series with the complementary metal-oxide-semiconductor half-effect transistor ON_6 It consists of resistors in parallel. One end of the 1235546 feedback circuit is connected to the input terminal of a differential amplifier and a solar amplifier, and one end is connected to the output of a differential amplifier. The output end can be connected to a buffer amplifier B before the input of the lower-level circuit, and the current sources are u, 12, 13 respectively. It is worth mentioning that the improved transimpedance amplifier ϋ improved circuit can also be changed to the common base circuit structure of the emitter input. The above X only describes the present invention in detail through a preferred embodiment, but any modifications and changes made to this embodiment, such as the type of the feedback circuit, the implementation of the current source circuit, etc., do not depart from the present invention. Spirit and scope. From the above detailed description, those skilled in the art can understand that this issuance can indeed achieve the aforesaid objectives, and that they have indeed complied with the provisions of the Patent Law and filed an application for an invention patent in accordance with the law. [Schematic description] Figure 1 is a schematic diagram of the circuit structure of a transimpedance amplifier. Figure 1 is a schematic diagram of a circuit structure of a transimpedance amplifier with a compensation capacitor and a control switch. Figure 3 is a transimpedance amplifier with a feedback resistor and a control switch. Schematic diagram of the circuit structure. Figure 4 is a schematic diagram of the circuit structure of a transimpedance amplifier using a two-stage amplifier circuit structure. Figure 5 is a circuit structure diagram of a transimpedance amplifier that is known to be achieved by a bipolar transistor circuit. Figure 7 shows the circuit structure of a transimpedance amplifier based on metal-oxide half-field effect transistor circuits. Figure 7 shows the circuit structure of the improved transimpedance amplifier circuit of the present invention. Figure 8 shows the improved circuit of the transimpedance amplifier of the present invention. Circuit Structure of Amplifying Circuit Structure 1235546 [Description of Symbols of Main Components] B Buffer Amplifier

Ipd photocurrent PD photodiode

Vout output voltage

Vref, Vref2 reference voltages Q1, Q2, Q5, Q6, Q7, Q8 bipolar transistor

Amp, Amp1, Amp2 amplifier

Rfb, Rfb1, Rfb2 feedback resistance

Cfb, Cfb1, Cfb2 Compensation capacitors SW1, SW2, SW3, SW4 switches 丨 1, 12, 丨 3, 丨 4, 丨 5, 丨 6 current source Q3, Q4 complementary metal-oxide-semiconductor field-effect transistors Φ1, Φ2, Φ3, Φ4, Φ5, Φ6 transistor switch

Claims (1)

1235546 10. Read Range: 1 · An improved circuit for a transimpedance amplifier, which includes:-a differential bipolar transistor amplifier, which amplifies H-the human end is connected to a photodiode, and An input terminal is connected to the reference voltage, and the feedback circuit is a capacitor connected in series with the complementary metal-oxide-semiconductor half-effect transistor and a capacitor connected in series with the complementary metal-oxide-semiconductor half-effect transistor. The resistance is composed of resistors connected in parallel. One end of the feedback circuit is connected to the input terminal of the differential bipolar transistor amplifier, and one end is connected to the output terminal of the differential bipolar transistor amplifier. Transistors and complementary metal-oxide-semiconductor half-field effect transistors have two structures to achieve high-speed response, low noise, and low power. 2 · The improved circuit of the transimpedance amplifier as described in item 1 of the scope of patent application, wherein the capacitance of the feedback circuit can be adjusted or removed according to actual needs. 3. The improved circuit of the transimpedance amplifier according to item 1 of the scope of the patent application, wherein a buffer amplifier can be connected to the output of the differential bipolar transistor amplifier. 12