Tuner for TV sets controlled by three diode group - has switching circuit with diodes and driver transistor connected through HF and LF coils to voltage controlled stage

摘要

The circuit has a series and two shunt diodes, and a driver transistor. Anodes of the circuit (5) shunt diodes are connected through a voltage divider (8, 24) or a series resistor (20) to the transistor (10) collector. Its emitter current is applied through an h.f choke (3) to the circuit (5) input (C). The series diode connects the input (C) with output (A). The transistor (10) collector is connected by a resistor (23) to the supply voltage terminal (UB). A resistor (21) is between the transistor (10) base and frame, and a resistor (22) between its base and the terminal (UB). A resistor (12) is inserted between the transistor (10) base and terminal (UR).