CS227162B1 - Inlet circuit of optoelectronic receiver with photodiode - Google Patents

Description

DESCRIPTION OF THE INVENTION

TO THE COPYRIGHT CERTIFICATE

CZECHOSLOVAK SOCIALISTIC

REPUBLIC (1B) 227162 (11) (B1)

ORAD FOR INVENTIONS DISCOVERY (22) Entries 28 10 81 (21) (PV 7886-81) (40) Published 26 08 83 (45) Published 15 06 86 (51) Int. Cl.3H 01 J 37/153 (75)

Author of the invention MRÁZ VLADIMÍR ing., KOSICE (54) Input circuit of optoelectronic receiver with photodiode

BACKGROUND OF THE INVENTION The present invention relates to a photodiode opto-opto input circuit of an opto-receiver, which is intended to receive modulated radiation in the presence of undesirable parasitic radiation.

So far, modulated radiation receiving circuits have the disadvantage that the sensitivity of the diode varies greatly due to the presence of strong ambient radiation of the orbosos.

The above-mentioned drawbacks are eliminated by the input circuit of the optoelectronic receiver with the photodiode according to the invention in that the first end of the photodiode is connected to the first end of the resistor, the second end of which is connected to the first pole of the power supply. whose co-connector is connected to a second power supply field and a base with a second end of the photodiode. At the same time, the first end of the base resistor is connected to this second end of the diode, the other end of which is connected to the base of the second transistor, the collector of which is connected to the nodal base of the first transistor, the second end of the photodiode and the first end. base resistance. The emitter of the second transistor coupled to the second power supply field is connected simultaneously to the first end of the capacitor, the second end of which is connected to the second power supply. The circuit output is considered to be the first transistor emitter.

By applying said circuit, it is achieved that the sensitivity of the photodiode optoelectronic receiver will be broadly independent of the radiation level of the radiation source such as the sun, room lighting, etc. The circuit also suppresses modulated parasitic radiation, as long as the harmonic modulation signal is less than the time constant of the input circuit, the more it is. The circuit time constant is given by the product of the input resistance of the second transistor and the capacitor. The advantage of the input circuit is high sensitivity, since the photodiode operates in a high ohmic load. However, the capacitance of the photodiode does not appear to be significant since it is connected between the base and the emitter of the first transistor. As a result, at the photodiode, less amplitude of the voltage than the amplitude of the output. This achieves the effect of photodiode capacity suppression. It incorporates a small output resistance, whose value is always less than the value of the first-resistance.

In the accompanying drawing, there is an embodiment of the invention where the photodiode 2 is the first

Claims (4)

The input circuit of the optoelectronic receiver with the photodiode is characterized in that the photodiode (2) is connected by a first end to the first end of the resistor (1j, the second end of which is connected to the first power pole (7)). an emitter of the first transistor a (4) whose collector is connected to the second power pole (8) and the base to the second end of the photodiode (2) and simultaneously to the first end of the base resistor (3) a second transistor (5), the collector of which is connected to the base node of the first transistor (4), the second end of the photodiode (2) and the first end of the base resistor (3j), and the emitter is connected to the second power pole (8); (5) is simultaneously connected to the first end of the capacitor (6), the second end of which is connected to the second power pole (8), the core output being the emitter of the first transistor (4).