Protection of input circuits of radio receivers. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / radio reception
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When a transistor radio operates at frequencies near which powerful radio stations operate, there is a danger of failure of the first transistor due to high voltages induced in the antenna. When using a common method of protection with two diodes connected in anti-parallel, with a large signal exceeding the level of 0.7 V, combinational noise appears. This can be avoided. using the diagram shown in the figure.
The protective circuit consists of a diode D1. capacitor C1 and resistors R1 and R2. From the divider R1R2, a small voltage is applied to the diode D1, closing it. When overloaded, the diode opens and the input circuit is shunted by capacitor C1, which significantly reduces the voltage of the signal applied to the base or gate of the transistor. The protection level in this device exceeds 0,7 V. It can be changed by selecting the resistances of resistors R1 and R2.
Silicon switching diodes can be used instead of the SAY10 diode.
Literature
- "Das elektron" (Austria), 1975, No. 12
Publication: N. Bolshakov, rf.atnn.ru
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