Frequency Discriminators Using Complementary Transistors

Two related frequency discriminators, one giving push-pull and the other single-ended output, are presented. The circuits are economical and noncritical; they use two complementary transistors, three resistors and four capacitors. Center frequency and bandwidth may be adjusted by variable resistors. A variety of input waveforms is acceptable. The performance is analyzed for rectangular signals and design curves are given. Other uses include bistable operation and frequency-selective gating.