| 摘要 |
PURPOSE:To facilitate a complicated control for a receivable range in a channel selection circuit, by fixing the lower limit of the tuning voltage that is applied to a tuner. CONSTITUTION:The voltage decided by the variable resistor VRn of the channel set according to the channel selection signal is applied to the base of the transistor TR. Thus the capacitor C is charged, and the voltage of the output terminal 5 increases up to a prescribed level. In case the voltage lower than the lowest voltage of 1.25V is applied to the base of the TR, no forward bias is applied between the base and the emitter of the TR. As a result, the TR is turned off and the voltage lower than 1.25V and given by the resistor VRn never emerges at the terminal 5. |
