JPH02295207A - Amplifier - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an amplifier device that can be used as a preamplifier of a receiving data link in an optical communication system.

[Conventional technology]

As a conventional amplifier of this type, IEEE Journal
al of' Solid-State
ts, Vol. SC-21No. 6 December
1986 r200 Mbit/s
7 7 Ibao Boutique Link Concentrator Circuit” “In
tegratedC1rcults f'or a 2
00Mbit/s Fiber-Optic Ilnk
” is known.

[Problem to be solved by the invention]

The conventional amplifier device described above has a problem in that it often causes free-running oscillation due to fluctuations in the output terminal voltage when a load is connected. In addition, external noise superimposed on the signal
There was a problem in that the signal was included in the output signal as it was and was output.

FIG. 3 shows a circuit diagram of a conventional amplifier device, and the above problems will be specifically explained. This amplifier device has an emitter follower transistor Q2 connected to the collector of an amplification stage transistor Ql whose emitter is grounded. transistor Q
From the emitter of 2, there is a diode D1 resistor R for backflow prevention.
, to the base of the transistor Q1.

Bi-eye voltage vcc of transistors Q 1 and Q 2 is provided from power supply section 300 .

In such an amplifier device, when a load is connected to the output terminal OUT, the current (2) flowing from the emitter of the transistor Q2 to the load side and the collector current I2 of the transistor Q2 fluctuate with alternating current fluctuations in the output terminal voltage V2. As a result, the collector current I of the transistor Q and the voltage V across the resistor r1. As a result, the gain of the amplifier constituted by the transistor Q1 becomes unstable.

Incidentally, in a receiving data link in optical communication, the gain of a preamplifier is often adjusted to just before oscillation. Therefore, when the amplifier shown in FIG. 3 is used under such conditions, free-running oscillation occurs due to gain instability. Further, when external noise is superimposed on a signal input from the input terminal IN, the signal is amplified as it is and taken out from the output terminal OUT, and the external noise is not removed.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an amplifier device that can prevent free-running oscillation and can also remove external noise superimposed on a signal.

[Means to solve the problem]

The amplifier device according to the present invention includes an amplifier section including an amplifier that amplifies an input signal with a predetermined gain, and an amplifier that is connected after the amplifier section and performs high and low impedance conversion between the amplifier and the load side. a first power supply unit that supplies a bias voltage to the amplifier unit; and a second power supply unit that supplies a bias voltage to the interface unit and operates independently of the first power supply. It is characterized by

Further, the amplifier device according to the present invention includes an amplifier section including an amplifier that amplifies an input signal with a predetermined gain, and an impedance conversion between high impedance and low impedance between the amplifier and the load side, which is connected to a subsequent stage of the amplifier section. The present invention is characterized in that it includes two stages of amplifiers that perform the following steps, and an interface section in which output terminals for obtaining differential outputs are led out from each of these amplifiers.

[Effect]

Since the amplifier device according to the present invention is configured as described above, in the former configuration, it is the interface section that is connected to the load, and the bias voltage is applied from the second power supply section independent of the amplifier section. Therefore, alternating current fluctuations in the voltage between the output terminals affect only the interface section, and the influence on the amplification section can be cut off.

Furthermore, since differential output of the output signal is obtained by the latter amplifier at the interface section, external noise superimposed on the signal is removed as an in-phase component.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An amplifier device according to an embodiment of the present invention will be described below with reference to FIGS. 1 and 2 of the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and the description thereof will be omitted.

FIG. 1 shows a configuration diagram of an amplifier device according to an embodiment of the present invention. The amplifying section 100 has the same configuration as the amplifying device shown in FIG. In this amplifying section 100, an input signal that has arrived at the input terminal IN is amplified with a predetermined gain by a transistor Ql, impedance-converted by an emitter follower transistor Q2, and sent to an interface section 2 o o.

The interface section 200 includes a two-stage emitter follower type transistor amplifier to which a bias voltage is applied by a power supply section 301 that operates independently of the power supply section 300 . That is, the signal output from the amplifier section 100 is applied to the base of the transistor Q3. A voltage corresponding to the input signal generated in the resistor R connected to the collector of the transistor Q3 is input between the collector and base of the transistor Q4,
leads to the output terminal OUT2. A signal passed through the transistor Q3 is outputted from a first output terminal OUT connected to the emitter of the transistor Q3. Here, transistor Q. Q is an emitter follower as described above, and is an amplifier with a gain of approximately "1" that performs high-to-low impedance conversion.

Further, a constant current load (constant current source) 101 is connected between the collector of the transistor Q3 and the ground. Let the current flowing through this constant current load 101 be I, and when the current voltage at each part is as shown in the figure, the collector voltage of the transistor Q3 is
Emitter voltage■. E is VCE″″V4-v3-(V-rl3)-rIcE CC . V −r(ICE+1)−rlcECC −V −2rIcE−rI CC −V CC 2 V a−r I −V −2 (V2−VBE) − r ICC .

Therefore, even when the output voltage v2 of the amplifier section 100 becomes too small (when the input current of the amplifier section 100 becomes too large), the current ■ flows through the constant current load 101, so that the collector
Emitter voltage V. E can be suppressed to prevent destruction of the transistor Q3. Because it has such characteristics, the interface section 200 can be connected to the amplifier section 1 that outputs any output signal.
Can also be connected to 00.

In the amplifier configured as above, the output terminal OUT
, OUT2, ■ Voltage between each output terminal v . ■ changes in alternating current, and the current 1. 1 fluctuates, current ■3, I5 also fluctuates. However, the interface section 200 is connected to the power supply section 3.
Since it is composed of a two-stage emitter follower that receives a bias voltage from a power supply unit 301 that operates independently of the power supply unit 301, the effect of high input impedance is directly exhibited.

That is, since the output terminal voltage V2 of the amplifying section 100 no longer fluctuates and the currents I 1 and I 2 also no longer fluctuate, the gain of the amplifying section 100 is stabilized and free-running oscillation can be prevented.

In addition, the interface unit 200 output terminals OUT, O
The output of UT2 becomes a differential output, and the dynamic phase component is removed.
External signals superimposed on the signal can be removed.

FIG. 2 shows a circuit diagram of an IC chip 400 in which the components of the above-mentioned amplifier device except for the power supply section are integrated into an IC. In this IC chip 400, the load capacitance, resistance, and inductance associated with the internal wiring from each of bins 1 to 6 are indicated by C, R, and L, respectively (even though they have the same symbols, they do not have the same values).

In this IC chip 400, an emitter follower transistor Q5 is connected to the front stage of the transistor Q1 in the amplifier section 100A, performs impedance conversion from high impedance to low impedance, and supplies a signal arriving from the input terminal IN to the base of the transistor Q1. Transistors Q and Q7 of the interface section 200 and the resistor connected thereto constitute a constant current load 101.

Specifically, the emitter potential is defined by the base potential of the transistor Q6, and by applying this to the base of the transistor Q7, the pace potential of the transistor Q7 is defined. As a result, the collector-base voltage of the transistor Q7 is actually stabilized, so that the collector current of the transistor Q7 becomes a constant current I.

Pin 3 of such an IC chip 400 is used as an input terminal IN, pin 4.5 is used as output terminals OUT1 and OUT2, a power supply 300 is connected to pin l, a power supply 301 is connected to pin 2, and pin 6 is connected to ground. Then, it operates as the amplifier shown in FIG. That is, even when a load is connected, the gain of the amplifier section 100A does not change, and free-running oscillation can be prevented, and since the output is a differential output, external noise can be removed from the signal. Therefore, this IC chip is suitable for use as a pre-amplifier IC for a receiving data link in optical communication.

Note that the transistor of this embodiment may be a unipolar transistor instead of a bipolar transistor, and the same effect can be expected even if the transistor is a vacuum tube.

〔Effect of the invention〕

As described in detail above, according to the amplifier according to the present invention, the amplifier section and the interface section are biased by the independently operating power supply section, so that the influence of AC fluctuations due to load connection is limited to the interface section. , since it does not affect the amplifier section, free-running oscillation can be prevented.

Further, since the output terminals are obtained from each of the amplifiers for impedance conversion to obtain a differential output, there is an effect that external noise superimposed on the signal can be removed.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an amplifier according to an embodiment of the present invention, Fig. 2 is a block diagram of an IC version of the amplifier according to an embodiment of the present invention, and Fig. 3 is a diagram of a conventional amplifier. FIG. 100,IOOA...Amplification section, 101...Constant current load, 200...Interface section, 300,301.
...Power supply section, 400...IC chip, Q-Q7.
...Transistor.

Claims (1)

[Claims] 1. An amplifier section including an amplifier that amplifies an input signal with a predetermined gain; and an amplifier section that is connected to a subsequent stage of this amplifier section and performs high and low impedance conversion between the amplifier and the load side. an interface section including an amplifier; a first power supply section that supplies a bias voltage to the amplification section; and a second power supply section that supplies a bias voltage to the interface section and operates independently of the first power supply. An amplifying device characterized by comprising: 2. An amplifier section including an amplifier that amplifies the input signal with a predetermined gain, and a two-stage amplifier connected to the rear stage of this amplifier section and performing high and low impedance conversion between the amplifier and the load side. , and an interface section whose output terminals for obtaining a differential output are drawn out from each of these amplifiers. 3. A first power supply unit that supplies a bias voltage to the amplification unit; and a second power supply unit that supplies a bias voltage to the interface unit and operates independently of the first power supply. The amplifying device according to claim 2, characterized in that: