Frequency synthesizer electronic tuning voltage for generating the low-pass filter circuit of the tuner

摘要

(57) [summary] [purpose] reception frequency is I get a low-pass filter that can quickly generate a tuning voltage also changed greatly. [Configuration] and a negative feedback circuit including a capacitor between the output side of the transistors constituting the inverting amplifier and the input side, The grounded emitter of the transistor, and connecting a load between the collector and a power supply. Connect the base of a transistor constituting an emitter follower amplifying stage to the collector of the transistor and to the emitter and base of the transistor of the emitter follower stage described above, it is formed between the emitter and base of the transistor of the emitter follower stage a diode having a connection polarity opposite to the connection polarity of the equivalent diode is I connected in parallel. And discharge operation of the capacitor in the negative feedback circuit that is performed at the time of descent of the received frequency, because the charging operation to be carried out from the power supply to the capacitor is performed early during the rise of the received frequency, changes are made of greatly reception frequencies change the operation of the receiving frequency is also performed in a short period of time.