GB1001266A - Reactance transfer circuits - Google Patents

Abstract

1,001,266. Transistor reactance circuits. PYE Ltd. May 11, 1962 [May 15, 1961], No. 17593/61. Heading H3R. The effective value of a capacitance or inductance in a two-terminal network is amplified by a transistor circuit and the emitter circuit includes an impedance whereby the emitter D.C. standing current and the magnification of the reactive element are held constant. A capacitor, if connected to the transistor base, its other end being connected to earth, to supply potential or to the collector, presents at its emitter or collector a capacitance multiplied by # the transistor amplifier gain. Two transistors may be D.C. coupled, emitter to base, to increase the gain to # 1 , # 2 , the product of the respective transistor gains. Further, a variable resistor, e.g. voltage variable diode, may be connected between the base of the second transistor and earth, to vary the gain and capacitance in a frequency modulator, wobbulator, variable filter or A.F.C. circuit. In Fig. 6A the output capacitance varies from C when R v = 0 to # 6 # 7 .C when R v is large. Alternatively R v , C b may be replaced by a frequency sensitive CR ladder circuit so that the output capacitance varies with frequency. An inductor in the emitter circuit of a transistor presents to an input to the base its inductance value multiplied by #.