The LA1230 provides most of the functions required in FM IF stages of an FM tuner. The IF amplifier/limiter stage is composed of three stages of level detectors and a drive circuit for extending the linearity range of the signal meter deflection. The FM detector stage consists of a double-balanced quadrature detector circuit and has an AF amplifier and a muting control as auxiliary circuits. The muting drive stage contains a level detector responsive to S/N in the carrier signal under a low signal input condition, a circuit to detect a DC output signal of an S-curve supplied from the FM detector during tuning-off operation, and a drive circuit, and operates to reduce inter-station noise and other noises such as transient sound which would be caused by muting operations (in conventional circuitry). The AFC output and tuning meter drive stage have an additional clamp circuit that clamps the output voltage to a level of +/-0.7 volts, thereby improving the AFC operation range, variations from the tuning meter deflection, and symmetrical characteristics for the above. A DC-stabilized circuit having approximately constant current consumption against a power supply voltage variation of 8.5 to 16 volts is also added.
