| 摘要 |
1,034,592. Transistor oscillators. RADIO CORPORATION OF AMERICA. Jan. 6, 1964 [Jan. 9, 1963], No. 602/64. Heading H3T. In a transistor Colpitts oscillator a resistor is connected in parallel with the frequency-determining resonant circuit of such a value as to reduce frequency variations caused by variations in voltage of the supply. In the circuit of Fig. 1, an increase in the voltage E applied at terminal 21 causes the base-emitter voltage to increase and this increases the capacitance between base and emitter but reduces the resistance. Such capacitance increases tend to reduce the frequency of oscillation both by virtue of the added capacitance to resonant circuit 12, 14, 16 and by virtue of the modification in the phase change taking place between base and emitter. The corresponding reduction in base-emitter resistance tends to alter the phase change in the opposite direction and hence compensate the frequency variation. Variable resistor 48 is adjusted so that a minimum frequency change is obtained with supply variations. Inductors 28 and 41 constitute radiofrequency chokes. Figs. 2 and 3 show modified forms of the circuit in which a piezo-electric crystal in series with a capacitor is used as the frequency-controlling element. |
