MC-1590 IF amplifier circuit diagram

Pictured are amplifiers based on the 1490 and 1590 chips. This circuit can work well in the VHF region (30~80MHz). The input signal is coupled to the IC through capacitor C1. The tuning function is realized by the parallel resonant circuit formed by C2 and L1. Capacitor C3 connects the unused differential input terminal of the 1590 chip to AC ground.

Figure MC-1590 IF amplifier circuit diagram

The output tuning in the figure reflects the differential output characteristics of the 1590 chip. The LC tuning circuit consists of the primary coil of T1 and capacitor C6 forming a parallel resonant circuit, which is connected between pin 5 and pin 6. The resistor across this tank circuit reduces the circuit's loaded Q, which broadens the circuit's frequency response.

The V+ power supply is connected to the V+ terminal of the chip, and at the same time, it is connected to pin 6 through the coil L. Pin 2 can be used as the AGO for gain control.