JP6698413B2 - Grounded emitter feedback amplifier circuit and transimpedance amplifier circuit - Google Patents

Description

  The present invention relates to a grounded-emitter feedback amplifier circuit using an emitter follower and a transimpedance amplifier circuit, for example, a grounded-emitter feedback amplifier circuit used in a transimpedance amplifier circuit mounted in a receiver in an optical communication system.

  Generally, in a receiver of an optical communication system, a received optical signal is subjected to light-current conversion to convert a current signal into a voltage signal, and the voltage signal is converted into a circuit in a subsequent stage (for example, an analog/digital converter and a digital signal processor). Etc.) is provided, and a transimpedance amplifier circuit (TIA: Transimpedance Amplifier) that linearly amplifies the voltage amplitude is provided.

  As an amplifier circuit applicable as a transimpedance amplifier circuit, for example, an amplifier circuit using a GaAs FET disclosed in Non-Patent Document 1 is known.

DERRY P.HORNBUCKLE,RORY L. VAN TUYL, “Monolithic GaAs Direct-Coupled Amplifiers”, IEEE Transactions on Electron Devices, Vol, ED-28, No,. 2, 1981, p.175-p.182. Edwin W. Greeneich, “Analog Integrated Circuits”, Springer-Science+Business Media, B.V, p67.

  The inventor of the present application studied the production of a grounded-emitter feedback amplifier circuit using an InP DHBT (Double Heterojunction Bipolar Transistor) as an amplifier circuit applied to a transimpedance amplifier circuit used in an optical communication system. As a result, it became clear that there are the following problems.

FIG. 17 is a diagram showing the configuration of a grounded-emitter feedback amplifier circuit that the present inventor has previously examined.
The grounded-emitter amplifier circuit 500 shown in FIG. 17 is a circuit based on the amplifier circuit of Non-Patent Document 1 and manufactured by replacing the FET with DHBT.

  In the grounded-emitter amplifier circuit 500, the base electrode of the transistor xqa20 forming the emitter follower is connected to the collector electrode of the transistor xqa10 forming the first grounded-emitter amplifier 50. The diode-connected transistor xqa201 is connected between the emitter electrode of the transistor xqa20 and the resistor R20 inserted in place of the constant current source, and is connected from the collector electrode of the transistor xqa10 that constitutes the first grounded-emitter amplification unit 50. The potential of is lowered. A feedback resistor Rf is connected between a node t2010 to which the diode-connected transistor xqa201 and the resistor R20 are connected and the base electrode of the transistor xqa10 that constitutes the first grounded-emitter amplification unit 50.

  In the grounded-emitter amplifier circuit 500, the collector potential of the transistor xqa10, that is, the potential of the output node t2 of the first grounded-emitter amplifier 50 is as high as about 2.1 V, and thus a level shift circuit for lowering the potential is required. ..

  As the level shift circuit, a circuit using two emitter followers shown in Non-Patent Document 2 can be exemplified. FIG. 18 shows another configuration example of the grounded-emitter amplifier circuit configured by using this level shift circuit.

  In the grounded-emitter amplifier circuit 600 shown in FIG. 18, the base electrode of the transistor xqa21 forming the second-stage emitter follower 62 is connected to the emitter electrode of the transistor xqa20 forming the first-stage emitter follower 61 (node t200). A feedback resistor Rf is connected between the emitter electrode of xqa21 and the base electrode of the transistor xqa10 that constitutes the grounded-emitter amplifier 60.

  However, in the grounded-emitter amplifier circuit 600 shown in FIG. 18, the potential of the node t200 can be lowered by adding the emitter follower 62 as a level shift circuit, but the configuration of the feedback circuit of the grounded-emitter amplifier 60 becomes complicated. Since the number of parts increases, the input conversion noise increases.

  As described above, the grounded-emitter amplifier circuits 500 and 600, which are examples of the preceding studies, have a problem that the circuit configuration is complicated and the input conversion noise tends to increase.

  The present invention has been made in view of the above problems, and an object of the present invention is to make it possible to suppress input conversion noise with a simpler circuit configuration and to have a high degree of freedom in designing a grounded-emitter amplifier circuit. To provide.

The grounded-emitter feedback amplifier circuit (100, 100A) according to the present invention has a first transistor (xqa10), and a grounded-emitter amplifier that amplifies a signal input to the base electrode of the first transistor and outputs the amplified signal from the collector electrode ( 11), a first feedback resistor (Rf1) connected between the base electrode of the first transistor and the collector electrode of the first transistor, and one end connected to the power supply and the other end connected to the collector electrode of the first transistor. An emitter having a connected first resistance and a second transistor (xqa20), which inputs a signal output from the collector electrode of the first transistor to the base electrode of the second transistor and outputs from the emitter electrode of the second transistor It has a follower output part (12) and a second feedback resistor (Rf2) connected between the emitter electrode of the second transistor and the base electrode of the first transistor.

The grounded-emitter feedback amplifier circuit further includes a third transistor (xqa201) connected in series with the first feedback resistor between the base electrode of the first transistor and the collector electrode of the first transistor. The collector electrode and the base electrode are connected to a node where the collector electrode of the first transistor and the base electrode of the second transistor are connected to form a diode connection, and one end of the first feedback resistor is connected to the emitter electrode of the third transistor. the other end of the first feedback resistor is connected to the base electrode of the first transistor.

In the grounded-emitter feedback amplifier circuit, the input resistance at the frequency of the signal input to the base electrode of the first transistor is approximately 50Ω according to the resistance value of the first resistor fixed to a predetermined value and the voltage of the power supply. made way, and as the voltage of the node where the base electrode of the collector electrode and the second transistor are connected to the first transistor is at least 1.43 V, the resistance value of the first feedback resistor and a second feedback resistor resistance Is set .

  In the grounded-emitter feedback amplifier circuit, the first transistor, the second transistor, and the third transistor may be bipolar transistors.

  A transimpedance amplifier circuit (1, 1A) used for optical communication according to the present invention has the above-mentioned grounded-emitter feedback amplifier circuit (100, 100A).

  In the above description, as an example, reference numerals in the drawings corresponding to the constituent elements of the invention are described in parentheses.

  According to the present invention, it is possible to realize a grounded-emitter amplifier circuit with a simpler circuit configuration, which can suppress input-equivalent noise and which has a high degree of freedom in design.

It is a figure which shows the structure of the amplifier containing the grounded-emitter feedback amplifier circuit which concerns on one embodiment of this invention. It is a figure which shows the amplifier circuit 30 which took out the basic element containing the 1st feedback path from the emitter common amplification part 11 of FIG. FIG. 3 is a diagram showing dependence of collector current Ic and collector potential Vc of transistor xqa10 on resistance Rf1 in amplifier circuit 30 of FIG. 2. FIG. 9 is a diagram showing the input signal frequency dependence of the voltage amplification factor with the resistance Rf1 as a parameter in the amplifier circuit 30 as an example of the first feedback path. FIG. 9 is a diagram showing the dependence of the voltage amplification factor Gain and the input conversion noise tinoise on the resistance Rf1 in the amplifier circuit 30 as an example of the first feedback path. FIG. 6 is a diagram showing the dependence of the input resistance zi on the resistance Rf1 in the amplifier circuit 30 as an example of the first feedback path. It is a figure which shows the amplifier circuit 40 which took out the basic element containing the 2nd feedback path from the grounded-emitter amplifier 11 of FIG. FIG. 9 is a diagram showing the dependence of collector current Ic and collector potential Vc of transistor xqa10 on resistance R2 in amplifier circuit 40 of FIG. 7. It is a figure which shows the structure of amplifier 1A containing another emitter grounded feedback amplifier circuit 100A which concerns on one embodiment of this invention. It is a figure which shows the frequency characteristic of the input resistance zi of 100 A of grounded-emitter feedback amplifier circuits. It is a figure which shows the voltage amplification factor of 100 A of grounded-emitter feedback amplification circuits. FIG. 6 is a diagram showing a voltage amplification factor of a grounded-emitter feedback amplification circuit 100 to which a diode-connected transistor xqa 201 is connected and a voltage amplification factor of an amplification circuit 40 to which only a feedback resistor Rf2 is connected. It is a figure which shows the simulation result by Hspice of the amplifier 1 containing the grounded-emitter feedback amplifier circuit 100 which concerns on one embodiment of this invention. It is a figure which shows the simulation result by Hspice of amplifier 1A containing the emitter grounded feedback amplifier circuit 100A which concerns on one embodiment of this invention. It is a figure which shows the simulation result by Hspice of the amplifier 5 containing the grounded-emitter feedback amplifier circuit 500 of a prior study example. FIG. 10 is a diagram showing a simulation result by Hspice of an amplifier 6 including a grounded-emitter feedback amplifier circuit 600 of a prior study example. It is a figure which shows the structure of the grounded-emitter feedback amplifier circuit which this inventor examined previously. It is a figure which shows the structure of another common-emitter feedback amplifier circuit which this inventor examined previously.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a configuration of an amplifier including a grounded-emitter feedback amplifier circuit according to an embodiment of the present invention.

  The amplifier 1 shown in the figure is, for example, an amplifier that amplifies a received signal and outputs it to a subsequent circuit in a receiver such as an optical communication system or a wireless communication system, and is, for example, a transimpedance amplifier circuit (TIA). .

  Although not particularly limited, the amplifier 1 can be realized by, for example, a semiconductor integrated circuit formed on a semiconductor substrate by a known InP DHBT manufacturing process. The amplifier 1 may be realized as a one-chip semiconductor device or a multi-chip semiconductor device, and is not particularly limited.

  The amplifier 1 amplifies the current signal input to the input terminal Pin and outputs it as a voltage signal Vout from the output terminal Pout. As shown in FIG. 1, the amplifier 1 is composed of a grounded-emitter feedback amplifier circuit 100 and an output stage amplifier circuit 200. In FIG. 1, reference numeral “Iin” is a current source.

  The output stage amplifier circuit 200 includes a common-emitter amplifier circuit including a transistor xqa30 and resistors R32 and R34, and a common-collector amplifier circuit (emitter follower) including a transistor xqa22, a resistor R22, and a capacitor Cout. The output stage amplifier circuit 200 amplifies the current signal amplified by the grounded-emitter feedback amplifier circuit 100 with a desired amplification factor and supplies it to the load resistor Rout connected to the output terminal Pout. As a result, the voltage signal Vout is generated.

  The grounded-emitter feedback amplification circuit 100 includes a grounded-emitter amplification unit 11, an emitter follower output unit 12, a transistor xqa201, and feedback resistors Rf1 and Rf2.

  The grounded-emitter amplification unit 11 includes a transistor xqa10 and a resistor R2. The emitter electrode of the transistor xqa10 is connected to, for example, the ground line GND to which a fixed voltage is supplied, and the base electrode of the transistor xqa10 is connected to the input terminal Pin. The resistor R2 has one end connected to the power supply line tv3 to which the power supply voltage V3 is supplied, and the other end connected to the collector electrode of the transistor xqa10.

  A feedback path including a resistor Rf1 and a transistor xqa201 is formed between the input and output of the grounded-emitter amplifier 11. Specifically, the resistor Rf1 and the diode-connected transistor xqa201 are connected in series between the collector electrode and the base electrode of the transistor xqa10. More specifically, the collector electrode and the base electrode of the transistor xqa201 are connected to the node t2 to which the resistor R2 and the collector electrode of the transistor xqa10 are connected, and the resistor Rf1 is connected to the input terminal Pin and the base electrode of the transistor xqa10. Connected between the node t1 and the emitter electrode of the transistor xqa201.

  The emitter follower output unit 12 includes a transistor xqa20 having a collector grounded and a resistor R20. The collector electrode of the transistor xqa20 is connected to the power supply line tv3, and the base electrode of the transistor xqa20 is connected to the node t2. The resistor R20 has one end connected to the ground line GND and the other end connected to the emitter electrode of the transistor xqa20.

  Between the output of the emitter follower output section 12 and the input of the grounded-emitter amplification section 11, a feedback path formed of a resistor Rf2 is formed. Specifically, the resistor Rf2 is connected between the node 200 to which the emitter electrode of the transistor xqa20 and the resistor R20 are connected and the input terminal Pin (node t1).

  As described above, in the grounded-emitter feedback amplifier circuits 100 and 100A according to the embodiment of the present invention, the first feedback path (resistor Rf1 and transistor xqa201) formed between the input and output of the first-emitter grounded amplifier unit 11 is used. , Or a resistor Rf1 only) and a second feedback path (Rf2) formed between the output of the emitter follower output section 12 in the next stage and the input of the grounded-emitter amplification section 11 in the first stage. Type circuit configuration. As a result, the grounded-emitter feedback amplifier circuits 100 and 100A can suppress input-equivalent noise with a simpler circuit configuration and can arbitrarily set the collector potential of the first-stage transistor. The operation and effects of the grounded-emitter feedback amplifier circuits 100 and 100A will be described in detail below.

First, the features of each of the two return paths described above will be described.
FIG. 2 is a diagram showing an amplifier circuit 30 in which basic elements including the first feedback path are taken out from the grounded-emitter amplifier 11.
The amplifier circuit 30 shown in FIG. 2 is an example of an amplifier circuit including a first feedback path, and a resistor Rf1 as a first feedback circuit is provided between the collector electrode and the gate electrode of the grounded-emitter transistor xqa10. It is a circuit connected by. That is, it is a circuit in which the transistor xqa201 of the grounded-emitter amplifier 11 shown in FIG. 1 is removed and the resistor R4 is connected to the emitter electrode of the transistor xqa10.

  FIG. 3 is a diagram showing the dependence of the collector current Ic of the transistor xqa10 and the collector potential Vc on the resistance Rf1 in the amplifier circuit 30 of FIG.

  In FIG. 3, reference numerals 400 and 401 are simulation results by Hspice when Vcc=5 V, R2=2.5 kΩ, R4=0 Ω and the resistance Rf1 is changed as a parameter. Reference numeral 400 represents the collector potential Vc of the transistor xqa10, that is, the potential V(t2) of the output node t2 of the amplifier circuit 30, and reference numeral 401 represents the collector current Ic of the transistor xqa10.

  As understood from FIG. 3, in the amplifier circuit 30, when the resistance Rf1 is lowered, the collector current Ic of the transistor xqa10 increases. That is, in the amplifier circuit 30, by reducing the value of the resistor Rf1, the collector current Ic can be increased without changing the value of the resistor R2. However, by reducing the resistance Rf1, the collector potential Vc, that is, the potential V(t2) of the output node t2 of the amplifier circuit 30 decreases. For example, when Rf1 is 3 kΩ, the collector potential Vc of the transistor xqa10, that is, the voltage of the output node t2 is about 0.8V.

  FIG. 4 is a diagram showing the input signal frequency dependence of the voltage amplification factor of the amplifier circuit 30 using the resistor Rf1 as a parameter.

  In FIG. 4, reference numerals 410 to 413 are simulation results by Hspice when Vcc=5 V, R2=2.5 kΩ, R4=0 Ω and the resistance Rf1 was changed as a parameter. Reference numeral 410 represents the voltage amplification factor of the amplifier circuit 30 when Rf1=1 MΩ, reference numeral 411 represents the voltage amplification factor of the amplifier circuit 30 when Rf1=10 kΩ, and reference numeral 412 represents Rf1=3 kΩ. Represents the voltage amplification factor of the amplification circuit 30, and reference numeral 413 represents the voltage amplification factor of the amplification circuit 30 when Rf1=1 kΩ. Here, the voltage amplification factor is a voltage ratio [dBV] between the node t1 and the output node t2 in the amplifier circuit 30.

As understood from FIG. 4, the voltage amplification rate when the resistor Rf1 is changed, when the R f1 = 10 k.OMEGA, the maximum.

  FIG. 5 is a diagram showing the dependence of the voltage amplification factor Gain and the input conversion noise tinoise of the amplifier circuit 30 on the resistance Rf1.

  5, in the amplifier circuit 30, reference numerals 421 and 422 denote Vcc=5V, R2=2.5 kΩ, R4=0 Ω, the frequency of the input signal (input frequency) is 1 MHz (hereinafter also referred to as center), and resistors It is a simulation result by Hspice when changing with Rf1 as a parameter. Reference numeral 421 is a simulation result gain(center) of the voltage amplification factor of the amplifier circuit 30, and reference numeral 422 is a simulation result of the integrated value tinoise of the input conversion noise (inoise) at each input signal frequency at the terminal t1. is there. Further, reference numeral 420 is a theoretical value gain(cal) of the voltage amplification factor calculated from the equivalent circuit of the amplifier circuit 30.

  As understood from FIG. 5, when the feedback resistance Rf1=10 kΩ, the voltage amplification factor becomes maximum and the input conversion noise becomes minimum.

  FIG. 6 is a diagram showing the dependence of the input resistance zi in the amplifier circuit 30 on the resistance Rf1.

  In FIG. 6, reference numeral 430 indicates the absolute value V(t1)m of the voltage appearing at the terminal t1 when one unit of alternating current (input frequency: 1 MHz) is injected into the terminal t1 as the input resistance zi of the amplifier circuit 30. It is a simulation result zi(center) by the evaluated Hspice, and a reference numeral 431 represents a theoretical value of the input resistance zi(cal) of the amplifier circuit 30 calculated from the equivalent circuit of the amplifier circuit 30.

  As understood from FIG. 6, the input resistance zi of the amplifier circuit 30 increases in proportion to the feedback resistance Rf1. For example, when the feedback resistance Rf1 is set to "10 kΩ" so that the voltage amplification factor of the amplifier circuit 30 is maximum and the input conversion noise is minimum, the input resistance zi of the amplifier circuit 30 is about 133 Ω according to FIG. .

  By the way, when the amplifier circuit 30 is used as, for example, a transimpedance amplifier circuit used in optical communication, the input resistance zi is required to have a constant value (for example, 50Ω). For example, when the input resistance zi of the transimpedance amplifier circuit is required to be “50Ω”, the feedback resistance Rf1 must be smaller than 3 kΩ from FIG. However, when the feedback resistance Rf1 becomes smaller than “10 kΩ”, the voltage amplification factor of the amplifier circuit 30 decreases and the input conversion noise increases, as shown in FIG.

  As described above, according to the grounded-emitter amplifier circuit 30 in which the first feedback path connecting the collector electrode and the gate electrode of the grounded-emitter transistor xqa10 with the resistor Rf1 is formed, the resistance R2 is not changed. There is an advantage that the voltage of the output node t2 of the amplifier circuit 30 can be set by the feedback resistor Rf1.

  On the other hand, when the amplifying circuit 30 is used as the amplifying unit in the input stage of the transimpedance amplifying circuit used in optical communication, the input resistance zi must be set to a constant value (for example, 50Ω), and therefore the feedback resistance Rf1 However, there is a demerit that the voltage amplification factor is lowered and the input conversion noise is increased. Further, by reducing the feedback resistor Rf1, the output node t2 of the amplifier circuit 30 is lowered, so that there is a demerit that it becomes difficult to connect the emitter follower and the grounded-emitter amplifier to the subsequent stage of the amplifier circuit 30. For example, in order to connect the output stage amplifier circuit 200 shown in FIG. 1 to the subsequent stage of the amplifier circuit 30, the potential of the output node t2 of the amplifier circuit 30 needs to be at least 1.43V.

Next, the second feedback path will be described.
FIG. 7 is a diagram showing an amplifier circuit 40 in which the basic elements including the second feedback path are taken out from the grounded-emitter amplifier 11 of FIG.

  The amplifier circuit 40 shown in FIG. 7 is an example of an amplifier circuit including a second feedback path, and includes a transistor xqa20 and a resistor R20 at an output node t2 of a grounded-emitter circuit including resistors R2, R4 and a transistor xqa10. A circuit in which the emitter follower is connected and a resistor Rf2 as a second feedback circuit is connected between the output node t200 of the emitter follower and the input terminal Pin of the grounded-emitter circuit. That is, it is a circuit in which the feedback resistor Rf1 and the transistor transistor xqa201 of the grounded-emitter feedback amplifier circuit 100 shown in FIG. 1 are removed, and the resistor R4 is connected to the emitter electrode of the transistor xqa10.

  FIG. 8 is a diagram showing the dependence of the collector current Ic of the transistor xqa10 and the collector potential Vc on the resistor R2 in the amplifier circuit 40.

  In FIG. 8, reference numerals 450 and 451 set the feedback resistance Rf2 so that the input resistance zi of the amplifier circuit 40 falls within 49 to 50Ω, set Vcc=5V, R4=0Ω, and change the resistance R2 as a parameter. It is a simulation result by Hspice at the time. Reference numeral 450 represents the collector current Ic of the transistor xqa10, and reference numeral 451 represents the collector potential Vc of the transistor xqa10, that is, the potential V(t2) of the node t2.

  As understood from FIG. 8, since the feedback resistance Rf2 is fixed so that the input resistance zi of the amplifier circuit 40 becomes about 50Ω, the resistance R2 is changed in order to change the collector current Ic of the transistor xqa10. I have to let That is, in order to increase the collector current Ic in the amplifier circuit 40, it is necessary to make the resistance R2 smaller than in FIG. This means that V(t2)>>1.43V, and a decrease in R2 results in a decrease in amplification factor and an increase in input conversion noise.

  Further, in order to connect the output stage amplifier circuit 200 to the subsequent stage of the amplifier circuit 40, as described above, the collector potential Vc (V(t2)) of the transistor xqa10 needs to be 1.43 V or more. 1.43 V is where the resistance R34 of the output stage amplifier circuit 200 becomes zero. In order to set the collector potential Vc of the transistor xqa10 to 1.43 V (solid line arrow in FIG. 8), it is necessary to set the resistance R2 to 7 kΩ or more as shown in FIG. However, if the resistance R2 is 7 kΩ or more, the collector current Ic decreases, and thus the band of the amplifier circuit 40 may decrease.

  Further, in the amplifier circuit 40, the feedback resistance Rf2, the collector current Ic of the transistor xqa10, and the collector potential Vc (V(t2)) are inevitably determined by the conditions of the input resistance zi=50Ω and the resistance R2. It has the disadvantage of low flexibility.

As described above, both the amplifier circuit 30 and the amplifier circuit 40 lower the collector potential of the first stage grounded-emitter transistor (prompt simplification of the level shift circuit), but are suitable for use as a transimpedance amplifier circuit for optical communication. I can't say.
For example, as a transimpedance amplifier circuit for optical communication, a case where a collector current Ic of the first stage transistor xqa10>1 mA, a collector potential V(t2)>1.43 V of the transistor xqa10, and an input resistance zi=50Ω are required. Think

  In this case, the amplifier circuit 30 having the first feedback path can satisfy Ic>1 mA for the above-mentioned reason, but can simultaneously satisfy V(t2)>1.43V and the input resistance zi=50Ω. Can not.

  On the other hand, the amplifier circuit 40 having the second feedback circuit can satisfy the input resistance zi=50Ω, Ic>1 mA, and the collector potential V(t2)>1.43V for the reasons described above. However, the collector potential V(t2)>>1.43V and the voltage becomes too high. Therefore, when the output stage amplifier circuit 200 is connected to the subsequent stage (output node t200) of the amplifier circuit 40, the level shift circuit is connected to the collector electrode (node t2) of the transistor xqa10 in the first stage, or the output stage amplifier circuit is connected. It is necessary to connect the resistor R34 shown in FIGS. 17 and 18 to the emitter electrode of the transistor xqa30 of 200 as an emitter resistor, and as a result, the number of parts increases or the resistor R34 having a large resistance value is selected. As a result, the total input conversion noise may increase.

Therefore, in the grounded-emitter feedback amplifier circuits 100 and 100A according to the present invention, as shown in FIGS. 1 and 9, the above-described first feedback path and second feedback path are formed, and a double feedback type circuit configuration To do.
Specifically, first, as shown in FIG. 9, in the grounded-emitter feedback amplifier circuit 100A, a resistor Rf1 is connected between the input and output of the first-emitter grounded amplifier unit 11 as a first feedback path.

  According to this, as described above, by adjusting the value of the feedback resistor Rf1, it is possible to determine the collector potential of the first-emitter-grounded transistor xqa10 without changing the value of the resistor R2.

  However, the requirements for the transimpedance amplifier circuit only with the first feedback path (for example, the collector current Ic of the first-stage transistor xqa10>1 mA, the collector potential V(t2) of the transistor xqa10>1.43 V, and the input resistance zi). When it is attempted to satisfy (.apprxeq.50 .OMEGA.), it is understood that such a condition does not exist, as is clear from FIGS.

  Therefore, in the grounded-emitter feedback amplifier circuit 100A, a resistor Rf2 is further provided as a second feedback path between the output node t200 of the emitter follower output section 12 in the next stage and the input terminal Pin of the first-emitter grounded amplification section 11. Connecting.

  According to this, the input resistance zi of the grounded-emitter feedback amplifier circuit 100A is set to 50Ω without lowering the voltage amplification factor (Av) of the grounded-emitter amplifier 11 in the first stage (without increasing the input conversion noise). It becomes possible. For example, as shown in FIG. 6, when the feedback resistance Rf1=10 kΩ, the voltage amplification factor of the first-stage grounded-emitter amplifier 11 (amplifier circuit 30) is maximum and the input conversion noise is minimum, so that the feedback resistance Rf1 Is set to “10 kΩ” to maximize the voltage amplification factor of the grounded-emitter amplifier 11 in the first stage. According to this, the input conversion noise of the grounded-emitter amplifier 11 can be reduced, and the value of the feedback resistor Rf2 (Rf2=50×(1+Av)) can be set large, so that the input of the feedback resistor Rf2 can be reduced. The contribution to reduced noise can be reduced. Further, by finely adjusting the value of the resistance Rf2, the input resistance zi can be set to 50Ω almost accurately.

Next, the frequency characteristics and voltage amplification factor of the input resistance zi of the grounded-emitter feedback amplifier circuit according to the present invention will be described in detail. Here, description will be made using a grounded-emitter feedback amplification circuit 100A as another embodiment of the present invention shown in FIG. 9 in which the diode-connected transistor xqa201 is removed from the grounded-emitter feedback amplification circuit 100.
FIG. 10 is a diagram showing frequency characteristics of the input resistance zi of the grounded-emitter feedback amplifier circuit 100A. Reference numeral 461 is a simulation result by Hspice of the input resistance zi of the grounded-emitter feedback amplifier circuit 100A when Rf1=10 kΩ, Rf2=4 kΩ, and R2=2.5 kΩ. As a comparative example, reference numeral 460 is a simulation result by Hspice of the input resistance zi of the circuit in which Rf1=10 kΩ, R2=2.5 kΩ, Rf2 of the grounded-emitter feedback amplifier circuit 100A is removed, and only Rf1 is connected.

  As understood from FIG. 10, when Rf1=10 kΩ, Rf2=4 kΩ, and R2=2.5 kΩ, the input resistance zi of the grounded-emitter feedback amplifier circuit 100A becomes 50Ω or less at the input frequency of 20 kHz to 500 MHz.

  Further, as described below, in the grounded-emitter amplifier circuit 100A, the influence on the voltage amplification factor and the input conversion noise by connecting the feedback resistor Rf2 in addition to the feedback resistor Rf1 is limited.

FIG. 11 is a diagram showing the voltage amplification factor of the grounded-emitter feedback amplifier circuit 100A.
Similar to FIG. 10, reference numeral 471 is a simulation result by Hspice of the voltage amplification factor of the grounded-emitter feedback amplifier circuit 100A when Rf1=10 kΩ, Rf2=4 kΩ, and R2=2.5 kΩ. Reference numeral 470 is, as a comparative example, Rf1=10 kΩ, R2=2.5 kΩ, the feedback resistor Rf2 is removed from the grounded-emitter feedback amplifier circuit 100A, and the simulation result by Hspice of the voltage amplification factor of the circuit in which only Rf1 is connected is shown. .

As can be seen from FIG. 11, the voltage amplification factor of the grounded-emitter feedback amplifier circuit 100A is slightly lower than the voltage amplification factor of the amplifier circuit without the feedback resistor Rf2 at a frequency of 10 kHz or higher. The input-equivalent noise tinoise of the grounded-emitter feedback amplifier circuit 100A (corresponding to 461 and 471) at this time is 3.667375963e-06A, and the input-equivalent noise tinoise of the amplifier circuit (460, 470) without the feedback resistor Rf2. Is 2.993814085e-06A, and the input conversion noise tinoise is 2.989076563e-06A when the input resistance zi is 50Ω only with Rf1 in the amplifier circuit without the feedback resistance Rf2. As understood from this, it can be said that the influence of the feedback resistor Rf2 in addition to the feedback resistor Rf1 on the voltage amplification factor and the input conversion noise is small.

  Therefore, by connecting the feedback resistors Rf1 and Rf2 as described above and appropriately setting the values of the feedback resistors Rf1 and Rf2, the input resistance zi can be set to 50Ω while suppressing the input conversion noise. ..

  However, when the feedback resistors Rf1 and Rf2 are set as described above, the potential of the output node t2 of the grounded-emitter amplifier 11 becomes about 0.9136 V, and the potential of the output node t200 of the emitter follower output unit 12 in the subsequent stage is about 0. Since it becomes 0.2136V (=0.9136-0.7), the output stage amplifier circuit 200 cannot be connected as it is.

  Therefore, in the grounded-emitter feedback amplifier circuit 100 according to the present invention, the diode-connected transistor xqa201 is further connected in series with the feedback resistor Rf1.

As a result, the voltage of the output node t2 of the grounded-emitter amplifier 11 in the first stage can be set to 1.43 V or higher, so that one emitter follower and one grounded emitter amplifier circuit are provided in the subsequent stage of the grounded emitter amplifier 11. It is possible to connect the output stage amplifier circuit 200 including In this case, the potential of the output node t2 (collector potential of the transistor xqa10) V(t2) of the grounded-emitter circuit of the first stage can be determined by Rf1 so as not to be >>1.43V, so that the output stage amplifier circuit 200 is The level shift required for connection is only one emitter follower (xqa20).
Also, by adjusting the value of the feedback resistor Rf1 connected to the diode-connected transistor xqa201, the bias of the first-stage transistor xqa30 of the output stage amplifier circuit 200 is set to a circuit configuration in which the resistor R34 is not connected (R34=0). It becomes possible.

  As described above, according to the grounded-emitter feedback amplifier circuit 100 according to the present invention, since the diode-connected transistor xqa201 is connected in series with the feedback resistor Rf1, the total number of components can be reduced as compared with the conventional case. It is possible to further reduce the input conversion noise.

  Further, as shown in FIG. 12, the grounded-emitter feedback amplifier circuit 100 in which the diode-connected transistor xqa201 is connected and the potential V(t2) of the node t2 is set to 1.43 V sets the potential of the node t2 to R2=7 kΩ. The band can be widened as compared with the amplifier circuit 40 in which V(t2) is set to around 1.43V.

  FIG. 12 is a diagram showing the voltage amplification factor of the grounded-emitter feedback amplification circuit 100 to which the diode-connected transistor xqa 201 is connected and the voltage amplification factor of the amplification circuit 40 to which only the feedback resistor Rf2 is connected.

  In the figure, reference numeral 481 is Rf1=7 kΩ, Rf2=4.2 kΩ, and R2=2.5 kΩ, and the voltage amplification factor of the grounded-emitter feedback amplifier circuit 100 when the transistor xqa201 is connected (node t1 and t200 It is a simulation result by Hspice of ratio of absolute value of voltage=V(t200)/V(t1). As a comparative example, reference numeral 480 represents the voltage amplification factor Hspice when Rf2 is set so that the input resistance zi=50Ω and the resistance R2=7 kΩ in the amplifier circuit 40 in which only the feedback resistor Rf2 is connected. It is a simulation result.

  As shown in FIG. 12, the band (-3 dB) of the grounded-emitter feedback amplifier circuit 100 is 3.464 GHz, and the band (-3 dB) of the amplifier circuit 40 is 1.2076 GHz. As understood from this, according to the grounded-emitter feedback amplifier circuit 100, the resistor R2 is adjusted in the amplifier circuit 40 in which only the feedback resistor Rf2 is connected to set the potential V(t2) of the node t2 to 1.43V. It becomes possible to widen the band as compared with the case of performing.

  As described above, according to the grounded-emitter feedback amplifier circuit 100 according to the present invention, the feedback circuit including the resistor Rf1 and the feedback circuit including the resistor Rf2 are used to double the input to the first-emitter grounded amplifier unit 11. By applying feedback, it is possible to arbitrarily set the collector potential (node t2) of the transistor xqa10 that constitutes the first-stage grounded-emitter amplification section 11, and to deteriorate the frequency characteristic of the first-stage grounded-emitter amplification section 11. Without it, it becomes possible to satisfy the condition of the input resistance zi required as a transimpedance amplifier circuit for optical communication.

  Further, in the grounded-emitter feedback amplifier circuit 100 according to the present invention, by connecting the diode-connected transistor xqa201 in series with the feedback resistor Rf1, it is possible to reduce the total number of parts as compared with the conventional case, and thus the input conversion noise is reduced. Further reduction is possible.

  Even if the diode-connected transistor xqa201 is not connected in series with the feedback resistor Rf1 as in the grounded-emitter feedback amplifier circuit 100A shown in FIG. 9, by adjusting the values of the resistors Rf1 and Rf2, the emitter of the first stage can be adjusted. It is also possible to set the potential V(t2) of the output node t2 of the ground amplification unit 11 to 1.43V or more. For example, when Rf1=45 kΩ and Rf2=3.65 kΩ, V(t2)≈1.44 V and Ic≈1.40 mA are obtained from FIG. As a result, the output stage amplifier circuit 200 can be connected without using a large resistance value for the resistor R34. In this case, the input resistance zi can be set to 50Ω by adjusting the resistance Rf2 as in the grounded-emitter feedback amplifier circuit 100.

  FIG. 13 is a diagram showing a simulation result by Hspice of the amplifier 1 including the grounded-emitter feedback amplifier circuit 100 according to the embodiment of the present invention. In the simulation of FIG. 13, in the amplifier 1, R2=2.5 kΩ, R20=400 Ω, Rf1=7 kΩ, Rf2=4.2 kΩ, R32=2.5 kΩ, R34=0 Ω, R22=400 Ω, Cout=0.1 μF, Rout=50Ω, and the input resistance zi was set to be 49 to 50Ω in the input signal frequency range of 20 kHz to 500 MHz. The input resistance at an input frequency of 20 kHz or less was 49Ω or less.

  FIG. 14 is a diagram showing a simulation result by Hspice of the amplifier 1A including the grounded-emitter feedback amplifier circuit 100A according to the embodiment of the present invention. In the simulation of FIG. 14, in the amplifier 1A, R2=2.5 kΩ, Rf1=45 kΩ, Rf2=3.6 kΩ, R20=400 Ω, R34=0 Ω, R32=2.5 kΩ, R22=400 Ω, Cout=0.1 μF, Rout=50Ω, and the input resistance zi was set to be 49 to 50Ω in the input signal frequency range of 20 kHz to 500 MHz. The input resistance at an input frequency of 20 kHz or less was 49Ω or less.

  FIG. 15 is a diagram showing a simulation result by the Hspice of the amplifier 5 including the grounded-emitter feedback amplifier circuit 500 of the previous study example. In the simulation of FIG. 15, in the amplifier 5, R2=2.5 kΩ, Rf1=2.9 kΩ, R20=2 kΩ, R21=400 Ω, R34=1 Ω, R32=2.5 kΩ, R22=400 Ω, Cout=0.1 μF, Rout=50Ω, and the input resistance zi was set to be 49 to 50Ω in the input signal frequency range of 20 kHz to 500 MHz. The input resistance at an input frequency of 20 kHz or less was 49Ω or less.

  FIG. 16 is a diagram showing a simulation result by the Hspice of the amplifier 6 including the grounded-emitter feedback amplifier circuit 600 of the previously studied example. In the simulation of FIG. 16, in the amplifier 6, R2=2.5 kΩ, Rf=3.1 kΩ, R20=10 kΩ, R21=400 Ω, R34=40 Ω, R32=2.5 kΩ, R22=400 Ω, Cout=0.1 μF, Rout=50Ω, and the input resistance zi was set to be 49 to 50Ω in the range of the input signal frequency of 20 kHz to 500 MHz. The input resistance at an input frequency of 20 kHz or less was 49Ω or less.

  13 to 16 show the simulation results of the potential of the main node, the collector current of the main transistor, and the input conversion noise when the input resistance zi=50Ω is set in each common-emitter feedback amplifier circuit. . Here, "total equal input noise" represents the integrated value tinoise of the input referred noise of each input frequency of each circuit as a whole, and "below t200" is the integrated value of the input referred noise of the grounded-emitter feedback amplifier circuits 100 and 100A. “Below t210” represents an integrated value tinoise of input-equivalent noise of the grounded-emitter feedback amplifier circuits 500 and 600.

  As can be understood from FIGS. 13 to 16, in the grounded-emitter feedback amplifier circuits 100 and 100A according to the present invention, the collector current Ic of the first-emitter grounded transistor xqa10 is 1.3 mA or more, and the resistance of the output-stage amplifier circuit 200 is increased. R34 can be 0Ω and 2Ω. As a result, compared to the grounded-emitter feedback amplifier circuits 500 and 600 of the previously studied example, the input conversion noise can be reduced to about half.

  In the amplifier 1, “R34=2Ω” is set because the simulation of HSPICE does not converge when “R34=0”. This is because when R34=0, a small current change between the emitter and the base causes a large change in the collector current. By setting a small value for R34 (in this simulation, 2Ω is set). It is presumed that abrupt changes in collector current are suppressed and the simulation tends to converge.

  Although the invention made by the present inventors has been specifically described based on the embodiments, the present invention is not limited thereto, and it goes without saying that various modifications can be made without departing from the scope of the invention. Yes.

  For example, the case where the transistors Q1 to Q10 are InP DHBTs is illustrated, but some or all of these transistors may be replaced with, for example, SHBT (Single HBT), a normal NPN bipolar transistor, or the like.

  1, 1A... Amplifier, 100, 100A... Common emitter feedback amplifier circuit, 200... Output stage amplifier circuit, 11... Common emitter amplifier section, 12... Emitter follower, Rf1, Rf2... Feedback resistors 10, R2, R20, R34, R22 , R32... Resistance, Rout... Load resistance, xqa201, xqa10, xqa20, xqa30, xqa22... Transistor, Cout... Capacitance, Pin... Input terminal, Pout... Output terminal, t2, t200... Node.

Claims (3)

A grounded-emitter amplifier having a first transistor, which amplifies a signal input to the base electrode of the first transistor and outputs the amplified signal from the collector electrode;
A first feedback resistor connected between the base electrode of the first transistor and the collector electrode of the first transistor;
A first resistor having one end connected to a power source and the other end connected to the collector electrode of the first transistor;
An emitter follower output section that has a second transistor, inputs the signal output from the collector electrode of the first transistor to the base electrode of the second transistor, and outputs the signal from the emitter electrode of the second transistor;
A second feedback resistor connected between the emitter electrode of the second transistor and the base electrode of the first transistor,
Further comprising a third transistor connected in series with the first feedback resistor between the base electrode of the first transistor and the collector electrode of the first transistor,
A collector electrode and a base electrode of the third transistor are connected to a node to which the collector electrode of the first transistor and the base electrode of the second transistor are connected, and are diode-connected;
One end of the first feedback resistor is connected to the emitter electrode of the third transistor, the other end of the first feedback resistor is connected to the base electrode of the first transistor,
In accordance with the resistance value of the first resistor fixed to a predetermined value and the voltage of the power supply, the input resistance at the frequency of the signal input to the base electrode of the first transistor is approximately 50Ω, and The resistance value of the first feedback resistor and the resistance value of the second feedback resistor are set so that the voltage of the node connecting the collector electrode of the first transistor and the base electrode of the second transistor becomes at least 1.43V. A grounded-emitter feedback amplifier circuit characterized by a set value. The grounded-emitter feedback amplifier circuit according to claim 1 ,
The grounded-emitter feedback amplifier circuit, wherein the first transistor, the second transistor, and the third transistor are bipolar transistors. An emitter grounded feedback amplifier circuit according to claim 1 or 2, transimpedance amplifier circuit for use in optical communication.