universal AFC

103 universal AFC This AFC is suitable for frequencies up 100 MHz and for use in frequency generators, waveform generators and all sorts of receiver. The amplitude of the signal to be controlled is first amplified in two transistor stages, T1 and T2, and then applied to the D input of bistable FF1. The clock input of this multivibrator is connected to the Q8 output of IC1 which is a 14-step counter and crystal-controlled oscil- lator. The frequency of this oscillator is 32.768 kHz, so that a square wave of frequency 64 Hz becomes available at output Q8 (pin 13). This is used to clock FF1 and the input signal is therefore sampled 64 times per second. Flip-flop FF2 is fed from output Q9 (pin 15) of IC1 to provide an output of 16 Hz at its 0 output. The trailing edges of the sampled signal and the leading edges of the 16 Hz signal are summed by C4, C5, Dl, R7 and R8 and applied to the inverting input of op-amp 1C3. The non-inverting input of the op-amp (and the junction of Dl and D2)...