JPS60177686A - Photo-electricity converter - Google Patents

Abstract

PURPOSE:To obtain a high reliability against noise infiltrating from the output terminal of a light-electricity converting IC, by interposing an emitter-follower- type transistor circuit between the output terminal of the IC and the output of the coverter. CONSTITUTION:The output terminal t3 of a light-electricity converting IC5 is connected to the base B of a transistor TR10. The collector C of the TR10 is connected to a power supply terminal t1 and the output of a case 7, and the emitter E is connected to the case through a resistance 11. Output of the light- electricity converter is took out from the contact point of the emitter E with the resistance 11. The case 7 is further connected to the ground. According to this constitution, any noise entering from the output is bypassed to the emitter resistance 11 and the collector C and therefore the noise level applied to the IC5 is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an optical-to-electrical converter in optical fiber transmission.

[Background technology]

Digital Optical-to-electrical conversion IC (0/E) in optical communications
The circuit configuration of the conversion IC (conversion IC) is generally as shown in FIG. The optical signal that enters the Pin photodiode 1 is converted into an electrical signal, but since the electrical signal level is low, it is amplified by the next stage amplifier circuit 2, and the output signal is divided into two systems, one of which is automatically It passes through an adjustable threshold circuit (ATC circuit) 3, is input to a comparator 4, and becomes a reference voltage. The other voltage is applied to the other input terminal of the comparator 4, compared with the reference voltage, and output as a signal of 0.1. Since the Pin photodiode 1 has high impedance, it is susceptible to induced noise. When the light receiving level is low, the impedance of the Pin photodiode 1 is the highest, and as shown in FIG. 2, the comparator reference voltage is the lowest, so the noise margin as a circuit is the lowest. Therefore, when trying to improve the above noise margin, it is possible to shield the entire O/E conversion circuit and provide a filter on the power supply line, but this cannot prevent noise from entering from the output terminal. There wasn't. In particular, there is a problem in that the noise resistance is low especially for the 0β conversion IC which is made into a single chip IC.

[Purpose of the invention]

The present invention has been made to improve the above points, and its purpose is to provide a highly reliable optical-to-electrical converter against noise that enters from the output terminal. .

[Disclosure of the invention]

The present invention will be explained below based on the drawings shown as examples.

FIG. 3 is a diagram showing the terminal relationship of the 0/FJ conversion IC, and the present invention is intended to prevent noise from entering from the output terminal.

FIG. 4 shows an embodiment of the present invention. O/E conversion IC5
An LC wire 6 is connected to the power supply terminal (3), which is connected to an external power supply via a feedthrough capacitor 8 provided at the outlet of the conductive case 7. The ground terminal @ is connected to the case 7 via a conductor 9 with low high frequency impedance. The output terminal θ is the base o3 of the transistor IO.
), and the collector of the transistor (O is connected to the output part of the case 7 of the power supply terminal ■, and the emitter ■ is connected to the case 7 via the resistor 11. The output is connected to the connection between the emitter ■ and the resistor 11 In addition, the case 7 is connected to the ground. With the above configuration, intrusion noise from the power supply can be prevented by the feedthrough capacitor 8 and the LC filter 6. Intrusion noise from the ground can be prevented by reducing the grounding impedance by the conductor 9. Intrusion noise from the output can be prevented by
Since the emitter resistor 11 and the output voltage are bypassed to the 0 side, the noise level applied to the 0/E conversion circuit C5 is reduced.

〔Effect of the invention〕

As described above, according to the present invention, an emitter follower type transistor circuit is interposed between the output terminal θ and the output of the photo-electric conversion IC 5.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a general optical-to-electrical conversion IC, Figure 2-
Hyokoichi is an input/output characteristic diagram of an IC for electrical conversion, FIG. 3 is an input/output terminal configuration diagram of an IC for optical-to-electrical conversion, and FIG. 4 is a circuit diagram of an optical-to-electrical converter according to an embodiment of the present invention. show. 5... Photo-electrical conversion IC17... Conductive case,
[0...Transistor, 11...Resistor. Patent applicant Matsushita Electric Works Co., Ltd. Patent attorney Toshimaru Takemoto (and 2 others) Figure 1 I Figure 52 □ λ Light amount (Light l @ number)

Claims (1)

[Claims] (1) Optical-electrical conversion IC and the above-mentioned optical-electrical conversion IC
The base is connected to the output of the transistor, the collector is connected to the power supply, and the emitter is connected to one end or the other end of a resistor that is grounded, and the whole is connected to the transistor. 1. An optical-to-electrical converter comprising a conductive case and a conductive case, and outputting an output of 1y from the emitter.