AM-FM demodulator for superheterodyne receiver - has two frequency modulation systems and selective limiter of regenerative type

摘要

The frequency modulated demodulator has two input signals which have the same nominal central frequency. It comprises an FM-filter (18) and transistor pairs (Q1, Q2) (Q8, Q8) and non-inverting different amplifiers with an output amplifying amplifier (Q10) in the emitter line. These circuits set a series of pulses of variable time. Each of the emitters of the input transistors is connected with an constant current source of about 130 muA. Output from the filter is rectified by diodes (D4D5) before amplification and transmission to the audio amplifier. The AM stage of the heterodyne system similarly includes an AM filter transistor amplifier and output amplifier. The combined system an AM-FM converter with AFC and ACC.