JPS60145719A - Differential light receiving circuit - Google Patents

Abstract

PURPOSE:To eliminate distortion even when a large optical signal is inputted, by connecting a grounded-collector circuit to a grounded-emitter circuit to feed back the output and connecting a diode-connected transistor Tr in parallel with a feedback resistance of the grounded-collector circuit. CONSTITUTION:The grounded-collector circuit consisting of a Tr 2 is connected to the grounded-emitter circuit consisting of a Tr 6 to feedback the output. A diode-connected Tr 19 is connected in parallel with a feedback resistance 4 of the grounded-collector circuit to form an amplifier. Similarly, another amplifier is formed with Trs 8 and 3, a resistance 9, and a diode-connected Tr 20. These two amplifiers are connected symmetrically and are operated as a differential amplifying circuit, and this differential amplifying circuit is driven by a constant current sources consisting of Trs 10-12.

Description

[Detailed Description of the Invention] [View and Objectives of the Invention] The present invention relates to a differential optical receiving circuit, and more particularly to a differential optical receiving circuit suitable for outputting a signal without distortion when an optical signal is input manually. It is something.

FIG. 1 is a circuit diagram of a conventional differential optical receiver circuit. 1st
In the figure, 1 is a photodiode that converts an optical signal into a current; 2, 3, 8, 8; 10 to 11 are transistors; 4,
5,7,9.13~1G.

18 is a resistor, 17 is a diode, and transistors 2 and 3
, 6 and 8. lO and 12. Resistors 4 and 9, 5 and 7 and 13
15 are symmetrically connected to form a differential amplifier. Further, a portion consisting of resistors 16 and 18 and diode 17 provides a reference voltage for operating transistors 10 to 12 as constant current sources.

In the circuit of FIG. 1, the output voltage VouL is expressed by the following equation.

Vout#l1nXRf=PinXηXRf (1)
Here, Iin; Input terminal Pin; Human power optical power R; Resistance value η of feedback resistors 4 and 9 ; Photoelectric conversion coefficient However, the circuit shown in FIG. When an optical signal with a voltage Vout is input manually, the base potential and collector potential of the transistor 8 are reversed, and the transistor operates in the saturation region, so that the optical signal is distorted, amplified, and output.

A, that is, the circuit shown in Figure 1 is such that YBE≧I group X and Rf is formed.
It has the disadvantage that distortion-free amplification can only be performed in the range 1+4 of χ, and the dynamic range is narrow.

The present invention has been made in view of the above, and its objectives are -
The differential type/L, "V:
I=times W8 to 1.

Overview of Akira Shizuko] The feature of the present invention is an optical receiving circuit that converts an optical signal into an electric signal using a light-receiving converter, and a collector-grounded circuit is connected to an emitter-grounded circuit. 1. Amplifying circuit 11 formed by connecting a diode-connected transistor in parallel to the feedback resistor of the collector grounding circuit v8, Q as a pair,
The circuit configuration is such that each differential amplifier circuit is driven by a controllable constant X current source.

(Example) Hereinafter, the present invention will be explained in detail using the example shown in FIG.
Explain.

FIG. 2 is a circuit diagram showing an embodiment of the differential optical receiver circuit of the present invention. The same parts as in FIG. In FIG. 2, transistor 1 is connected in parallel with feedback resistors 4 and 9, respectively.
9 and 20 are connected, and the other parts are the same as in FIG.

According to the circuit of FIG. 2, the output voltage VA is
When the voltage between the base and emitter of the transistor rises above VBE with respect to the base voltage of
It is possible to control it so that it is as follows. therefore,
Therefore, the output voltage VA1 and the voltage between the base and emitter of the transistor 20 are limited. At this time, the potential of the collector voltage of transistor 8 decreases by the output voltage VA, but it does not decrease below the Hessmi pressure. It can be amplified without

According to the embodiment of the present invention described above, (1) Pre-reception 11: Since the circuit has a limit effect,
Human light. It is possible to output a distortion-free signal even when using human power, and the dynamic range can be increased by 100%.

(2) The maximum width of 1 inch is 1 inch between the base and emitter of the transistor, so it is easy to connect to the subsequent circuit.

(() Is it possible to control one signal width using 91 transistors, or to reduce the circuit to a single circuit?

There is a drawback.

〔Effect of the invention〕

As explained above, according to the present invention, large light 1+J
It has the effect of expanding the dynamic range by outputting 4 degrees Celsius (+S) when using manual power for the bow.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a conventional differential optical receiver circuit, and FIG. 2 is a circuit diagram showing an embodiment of the differential A≦ circuit of the present invention.
be. i: Botodai auto. 2, 3. 6. 8. 10-1 1. 1≦1.
20: Transistor. 4.5.7.9.13-16.18: I (anti. 17; Taito.

Claims (1)

[Claims] 1) In an optical receiving circuit that converts an optical signal into a wire signal using a light receiving element, a common collector circuit is connected to a common emitter circuit to apply feedback, and a transistor is connected in parallel to a feedback resistor of the common collector circuit with a diode. symmetrically connect the amplifier circuits formed by connecting X and dynamic amplifier circuit l'8.
What is claimed is: 1. A differential optical receiving circuit, characterized in that the differential amplifier circuit is operated as a circuit, and has a circuit configuration in which the differential amplifier circuit is driven by a controllable constant current source.