GB891230A - Improvements in or relating to transistorized receiving circuit arrangements - Google Patents

Abstract

891,230. Transistor radio receivers. PHILIPS ELECTRICAL INDUSTRIES Ltd. Jan. 2, 1959 [Jan. 7, 1958], No. 204/59. Class 40(6). The necessity for neutralizizing the intermediate frequency amplifier stages of a transistor superheterodyne radio receiver is avoided by designing the input transformer and output transformer of the intermediate frequency amplifier to produce an appropriate mismatch and by using collector to base D.C. feedback. The Figure shows a receiver comprising a self oscillating frequency changer 1, an intermediate frequency amplitier 4, detector 5 and an audio frequency amplifier 6. The I.F. input transformer has a low Q primary circuit and a relatively high Q secondary circuit with a tap 11 which loosely couples the circuit to transistor 7. The output transformer has a high Q primary circuit 14 loosely coupled at 13 to the output transistor and a low Q secondary circuit 15. In addition, the intermediate frequency transformer 12 has a high Q primary winding and tappings loosely coupling the transformer to the adjacent transistors. Negative D.C. feedback is provided by collector resistors 16, 18 and feedback resistors 17, 19, the collector resistances being of sufficient magnitude to drop substantially half the supply voltage. It is suggested that inductive taps could replace the capacitive taps.