Gain controlled broadband intermediate frequency amplifier - has coupling transformer with damped secondary connected through capacitor to transistor base and at tap to transistor emitter

摘要

The IF amplifier has a transformer as interstage coupler and a voltage dependent impedance to control its gain. The voltage-dependent impedance (D) connects the emitter of a second transistor (Ts2) to a tapping on the secondary winding (S) of the coupling transformer (U). The collector of a first transistor (Ts1) is connected to one end of the primary winding (P). The base of the second transistor is connected via a capacitor (C1) to one end of the second winding. The control voltage to a second tapping (b) on the secondary. This second tapping is ground via a capacitor (C2). The secondary is shunted by a resistor (R2).