AFC circuit and IC of the same adapted for lower heterodyne conversion and upper heterodyne conversion

Year	Description
1993	Invention patented by Taiwa Okanobu on March 30th, 1993. Abstract: An automatic frequency control circuit comprises a variable reactance element connected to a resonance circuit of a local oscillation circuit of an FM receiver, an inverting amplifier to which a demodulation output of an FM demodulation circuit of the FM receiver is supplied, and series circuit of a first resistor and a capacitor connected to an output terminal of the inverting amplifier. A second resistor is connected between an input terminal of the inverting amplifier and a junction between the first resistor and the capacitor, and a circuit supplies a voltage obtained at the junction as an automatic frequency control voltage to the variable reactance element. The polarity of the automatic frequency control voltage is varied by selecting the value of the second resistor. When the automatic frequency control circuit is formed as an IC, the capacitor and the second resistor are formed as elements for external connection.
Source: selected by the editor from original sources.

Invention: AFC circuit and IC of the same adapted for lower heterodyne conversion and upper heterodyne conversion