JP3149911B2 - Preamplifier circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transimpedance type preamplifier circuit, and more particularly to a technique for improving high-frequency characteristics thereof.

[0002]

2. Description of the Related Art Optical fiber communication has a very wide band, and if this wide band can be fully utilized, large-capacity transfer becomes possible. Therefore, devices such as a receiver and a transmitter used for optical fiber communication or the like are required to have a wide band. Therefore, a transimpedance type preamplifier circuit is used for a preamplifier circuit of a receiver for optical communication.

Conventionally, this type of transimpedance preamplifier is disclosed in, for example, Japanese Patent Application Laid-Open No. Hei 5-110346, and "I.E.E.E.
Journal of Solid State Circuit, Vol. 30, No. 10, pp. 1051-1054 (IEEE
JOURNAL OF SOLID-STATE CI
RCUITS, VOL30, NO. 10, OCTOBE
R, 1995, pp 1051-1054) ”, etc., for the purpose of obtaining a wide band in transimpedance gain and obtaining a high dynamic range.

FIG. 6 is a circuit diagram showing an example of a conventional transimpedance type preamplifier circuit.

Referring to FIG. 6, a conventional preamplifier circuit 59 comprises a current-to-voltage conversion amplifier comprising a transistor 1 and a resistor 6 having a common emitter, and an emitter follower buffer comprising a transistor 2, a diode 31 and a resistor 7. A stage 20, a second emitter-follower buffer stage comprising a transistor 3 and a resistor 8, and a diode 31
, A feedback resistor 5 for connecting the emitter of the transistor 2 and the base of the transistor 1 via a resistor, and a voltage amplifying unit including a transistor 4 having a grounded emitter, a resistor 10 and a resistor 9.

The diode 31 of the emitter-follower buffer stage 20 is for adjusting the operating point of the transistor 2 and is not always necessary for operation.

[0007] The photodetector 18 converts the received optical signal into an electric signal and outputs it.

The conventional preamplifier circuit 59 converts the electric signal output from the photodetector 18 into an impedance and amplifies the electric signal to a constant voltage and outputs the amplified signal.

The preamplifier circuit 59 is constituted by an integrated circuit, and the connection to the outside is made via a bonding wire. Therefore, a DC bias voltage is applied to the emitter-follower buffer stage 20 from the power supply 27 provided outside the preamplifier circuit 59 via the bonding wire 13 and the lead wire 28. A bypass capacitor 17 is provided between the bonding wire 13 and the lead wire 28 to ground the collector of the transistor 2 constituting the emitter follower buffer stage 20 in an AC manner.

A DC bias voltage is similarly applied from a power supply 26 to a current-to-voltage conversion amplifier comprising a transistor 1 and a resistor 6 via a lead wire 30 and a bonding wire 12. A bypass capacitor 16 is provided between the bonding wires 12.

Further, an input signal from the photodetector 18 is also input to the base of the transistor 1 via the bonding wire 11, and a signal amplified by the transistor 4 is also output via the bonding wire 14. Also,
The photodetector 18 is also connected to the ground via the bonding wire 15.

Next, the operation of the conventional preamplifier circuit 59 will be described.

First, an optical signal received by the photodetector 18 is converted into an electric signal, and then input to the base of the transistor 1 to be amplified by current-voltage conversion.
After that, the impedance is converted by the emitter follower buffer stage 20 including the transistor 3 and the resistor 8 and the transistor 4
, And is output from the collector of the transistor 4.

In the conventional preamplifier circuit 59, the voltage between the terminals of the resistor 7 of the transistor 2 forming the emitter follower / buffer stage 20 is supplied to the base of the first stage transistor 1 via the feedback resistor 5 in parallel. By doing so, the input impedance of the preamplifier circuit 59 is reduced, and the transimpedance gain characteristic is broadened.

However, when the signal to be handled is in a high frequency range, the effects of the inductance of the bonding wire 13 and the parasitic capacitance between the base and the collector of the transistor 2 cannot be ignored, and the voltage between the terminals applied to the bonding wire 13 is reduced by the transistor. The parallel input is fed back via the parasitic capacitance between the base and the collector. Therefore, in the conventional preamplifier circuit 59, a bonding capacitor connecting the collector of the transistor 2 forming the emitter follower buffer stage 20 and the bypass capacitor 17 is used.
Due to the inductance of the wire 13 in the high frequency range, peaking and band degradation occur in the transimpedance gain characteristic.

FIG. 7 shows the preamplifier circuit 59 shown in FIG.
5 shows the results of numerical simulation of the transimpedance gain characteristics using the value of the inductance of the bonding wire 13 as a parameter.

FIG. 7 shows that the peaking and the deterioration of the band are caused in the transimpedance gain characteristic as the inductance of the bonding wire 13 in the high frequency range increases.

[0018]

In the above-mentioned conventional preamplifier circuit, a bonding capacitor for connecting a collector of a transistor constituting an emitter-follower buffer stage and a bypass capacitor for grounding the collector in an alternating-current manner.
There is a problem that peaking and band degradation occur in the transimpedance gain characteristic due to the influence of the wire inductance.

The present invention has been made in view of the above problems, and has as its object to provide a preamplifier circuit which suppresses peaking and has a flat and wide band transimpedance gain characteristic over a high frequency range. .

[0020]

To achieve the above object, a preamplifier circuit according to the present invention comprises an amplifier circuit, an emitter follower / buffer circuit for converting the output impedance of the amplifier circuit, and an emitter follower / buffer circuit. In a preamplifier circuit having an emitter of a transistor forming a circuit and a first feedback resistor connecting an input portion of the amplifying circuit, a base of the transistor forming an emitter follower buffer circuit is provided.
It has a second feedback resistor connecting between the collectors.

According to the present invention, a second transistor is provided between a base and a collector of a transistor constituting an emitter follower buffer circuit.
The effect of the inductance of the bonding wire in the high-frequency range is reduced by connecting the feedback resistor of FIG.

Therefore, the peaking of the transimpedance gain characteristic can be suppressed, and the dependence of the peaking on the inductance value of the bonding wire can be reduced.

According to an embodiment of the present invention, there is provided a resistor and a capacitor for connecting in series between a collector of the transistor constituting the emitter follower buffer circuit and ground.

According to the present invention, the effect of the inductance of the bonding wire in a high frequency range is reduced by connecting a resistor and a capacitor in series between the collector of the transistor constituting the emitter follower buffer circuit and the ground. It was done. Therefore, the effect of the band reduction caused by the bonding inductance can be reduced.

Further, the preamplifier circuit of the present invention comprises an amplifier circuit, an emitter follower / buffer circuit for converting the output impedance of the amplifier circuit, an emitter of a transistor constituting the emitter follower / buffer circuit, and the amplifier circuit. A pre-amplifier circuit having a first feedback resistor connecting the input portions of the above and a bypass capacitor for AC grounding a collector of a transistor forming the emitter follower buffer circuit, wherein the emitter follower buffer circuit is formed. A resistor and a capacitor are connected in parallel between the collector of the transistor and the bypass capacitor.

The present invention provides bonding in a high frequency range by connecting a resistor and a capacitor in parallel between the collector of a transistor constituting an emitter follower buffer circuit and a bypass capacitor for grounding the collector in an AC manner. -The effect of the inductance of the wire is reduced.

Therefore, the peaking of the transimpedance gain characteristic can be suppressed, and the dependency of the peaking on the inductance value of the bonding wire can be reduced.

According to an embodiment of the present invention, there is provided a resistor and a capacitor for connecting in series between a collector of the transistor constituting the emitter follower buffer circuit and ground.

According to the present invention, the effect of the inductance of the bonding wire in a high frequency range is reduced by connecting a resistor and a capacitor in series between the collector of the transistor constituting the emitter follower buffer circuit and the ground. It was done.

Therefore, the effect of the band reduction caused by the bonding inductance can be reduced.

[0031]

Next, an embodiment of the present invention will be described in detail with reference to the drawings.

(First Embodiment) FIG. 1 is a circuit diagram of a preamplifier circuit according to a first embodiment of the present invention. The same numbers as those in FIG. 6 indicate the same components.

The preamplifier circuit 19 according to the present embodiment has the structure shown in FIG.
In the conventional preamplifier circuit, a feedback resistor 21 for connecting the collector and the base of the transistor 2 is provided.

In the preamplifier circuit 19 of the present embodiment, when a DC bias voltage is applied to the collector of the transistor 2 constituting the emitter follower / buffer stage 20, the bypass capacitor 17 is used to ground the collector AC.
However, in order to reduce the influence of the inductance of the bonding wire 13 connecting the bypass capacitor 17 and the collector of the transistor 2, the transistor 2
Are connected by a second feedback resistor 21 between the collector and the base.

Next, the effect of the preamplifier circuit 19 of this embodiment will be described.

FIG. 2 shows the preamplifier circuit 19 shown in FIG.
5 shows the results of numerical simulation of the transimpedance gain characteristics using the value of the inductance of the bonding wire 13 as a parameter.

When FIG. 2 is compared with FIG. 7, which is a result of numerical simulation of the transimpedance gain characteristic of the conventional preamplifier circuit 59 of FIG. 6, the preamplifier circuit 19 of this embodiment can suppress peaking. And the peaking bonding wire 1
It can be seen that the dependence on the inductance value of No. 3 is weak.

As a result, in the preamplifier circuit of the present embodiment, a flat transimpedance gain characteristic can be obtained over a high frequency range, so that jitter, ringing and circuit oscillation of an output waveform can be suppressed.
Good optical signal detection and reception are possible.

(Second Embodiment) FIG. 3 is a circuit diagram of a preamplifier circuit according to a second embodiment of the present invention.

Referring to FIG. 3, the preamplifier circuit 29 of the present embodiment differs from the circuit configuration of the preamplifier circuit of the first embodiment of FIG. 1 in that a resistor 22 and a capacitor are connected between the collector of the transistor 2 and the ground. A bypass circuit connected in series at 23 is provided.

The effect of the present embodiment, in addition to the effect of the above-described first embodiment, is to reduce the effect of the band reduction caused by the inductance in the high frequency range due to the bonding wire.

(Third Embodiment) FIG. 4 is a circuit diagram of a preamplifier circuit according to a third embodiment of the present invention.

Referring to FIG. 4, the preamplifier circuit 39 of the present embodiment is different from the conventional preamplifier circuit 59 of FIG. 6 in that the resistor 24 for connecting the collector of the transistor 2 and the bonding wire 13 in parallel with the resistor 24 is provided. Capacitor 25
Is provided.

In the preamplifier circuit 39 of this embodiment, when a DC bias voltage is applied to the collector of the transistor 2 constituting the emitter follower / buffer stage 20, the bypass capacitor 17 is used to ground the collector AC.
However, in order to reduce the influence of the inductance in a high frequency range due to the bonding wire 13 connecting the bypass capacitor 17 and the collector of the transistor 2, a resistor 24 is connected between the collector of the transistor 2 and the bonding wire 13. The capacitors 25 are connected in parallel.

The effect of the preamplifier circuit 39 of this embodiment is that peaking in the transimpedance gain characteristic can be suppressed, as in the first embodiment.
Further, the dependency of the peaking on the inductance value in a high frequency range by the bonding wire 13 is reduced.

(Fourth Embodiment) FIG. 5 is a circuit diagram of a preamplifier circuit according to a fourth embodiment of the present invention.

Referring to FIG. 5, the preamplifier circuit 49 of the present embodiment differs from the circuit configuration of the preamplifier circuit of the third embodiment of FIG. 4 in that a resistor 22 and a capacitor are connected between the collector of the transistor 2 and the ground. A bypass circuit connected in series at 23 is provided.

The effect of the present embodiment, in addition to the effect of the third embodiment, is to reduce the effect of the band reduction caused by the inductance in the high-frequency range by the bonding wire 13.

In the first to fourth embodiments, the amplifying sections at the first stage and the last stage are constituted by one transistor. However, the present invention is not limited to this structure. A combination of a plurality of transistors may be used.

The circuit configuration according to the first to fourth embodiments includes a single-stage amplifier on the input side, an emitter follower
Although two stages of buffers and one stage of output side amplification unit were used, the number of input side amplification stages may be two or more stages, the number of emitter follower / buffer stages may be one or more, and the number of output side amplification units may be one or more. It may or may not be necessary.

[0051]

As described above, the present invention can suppress the peaking in the transimpedance gain characteristic, and can reduce the inductance value of the bonding wire connecting the collector of the transistor of the emitter follower buffer circuit and the bypass capacitor. This has the effect of weakening the dependence of peaking.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a preamplifier circuit according to a first embodiment of the present invention.

FIG. 2 is a diagram showing transimpedance characteristics of a preamplifier circuit 19 of FIG. 1 using an inductance 13 as a parameter.

FIG. 3 is a circuit diagram of a preamplifier circuit according to a second embodiment of the present invention.

FIG. 4 is a circuit diagram of a preamplifier circuit according to a third embodiment of the present invention.

FIG. 5 is a circuit diagram of a preamplifier circuit according to a fourth embodiment of the present invention.

FIG. 6 is a circuit diagram of a conventional preamplifier circuit.

7 is a diagram showing transimpedance characteristics of the conventional preamplifier circuit 59 in FIG. 6 with the inductance 13 as a parameter.

[Explanation of symbols]

 1-4 transistor 5 feedback resistor 6-10 resistor 11-15 bonding wire 16, 17 bypass capacitor 18 photodetector 19 preamplifier circuit 20 emitter follower buffer stage 21 feedback resistor 22 resistor 23 capacitor 24 resistor 25 capacitor 26, 27 power supply 28 Lead wire 29 Preamplifier circuit 30 Lead wire 31 Diode 39 Preamplifier circuit 49 Preamplifier circuit 59 Preamplifier circuit

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ identification code FI H04B 10/26 10/28 (58) Fields investigated (Int.Cl. ⁷ , DB name) H03F 1/00-3/72 H04B 10/06

Claims (4)

(57) [Claims] An amplifier circuit for amplifying the electric signal from a photodetector for converting a received optical signal into an electric signal; an emitter follower / buffer circuit for performing an impedance conversion of an output impedance of the amplifier circuit; comprising a first and a feedback resistor connecting the input of the emitter and the amplifier circuit of the transistors constituting the follower Baffua circuit, Kore of the emitter follower buffer circuit
And Kuta, the preamplifier circuit between are connected by bonding wires with a bypass capacitor for AC grounded collector of transistors constituting the emitter follower buffer circuit, constituting the emitter follower buffer circuit A preamplifier circuit having a second feedback resistor connecting between a base and a collector of the transistor. 2. The preamplifier circuit according to claim 1, further comprising a resistor and a capacitor for connecting in series between a collector of said transistor constituting said emitter follower buffer circuit and ground. 3. An amplifier circuit for amplifying the electric signal from a photodetector for converting a received optical signal into an electric signal, an emitter follower / buffer circuit for performing impedance conversion of an output impedance of the amplifier circuit, and the emitter comprising a first and a feedback resistor connecting the input of the emitter and the amplifier circuit of the transistors constituting the follower Baffua circuit, Kore of the emitter follower buffer circuit
And Kuta, the preamplifier circuit between are connected by bonding wires with a bypass capacitor for AC grounded collector of transistors constituting the emitter follower buffer circuit, constituting the emitter follower buffer circuit A preamplifier circuit, comprising: a parallel circuit including a resistor and a capacitor, connected between the collector of the transistor and the bonding wire. 4. The preamplifier circuit according to claim 3, further comprising a resistor and a capacitor for connecting in series between a collector of said transistor constituting said emitter follower buffer circuit and ground.