Oscillator including a transistor used both as constant current source and amplifier

摘要

PCT No. PCT/JP86/00359 Sec. 371 Date Apr. 10, 1987 Sec. 102(e) Date Apr. 10, 1987 PCT Filed Jul. 14, 1986 PCT Pub. No. WO87/00993 PCT Pub. Date Feb. 12, 1987.The local oscillation circuit in accordance with the present invention is characterized as follows. The collector of an oscillation transistor is grounded for atlernating current. A series resonance circuit consisting of a variable capacitance diode and a resonator is connected to the base of the oscillation transistor. The other end of the series resonance circuit is grounded for alternating current. The emitter of the oscillation transistor is connected to the collector of an amplifying transistor. The emitter is grounded through a capacitor that removes or reduces the a.c. component and passes the d.c. component. An oscillation signal taken from the emitter of the oscillation transistor is fed to the base of the amplifier transistor. A local oscillation output signal is taken from the collector of the amplifier transistor, and bias potential to the amplifier transistor is impressed from the power source to the base of the amplifier transistor. With this arrangement, the current in the oscillation transistor is stabilized, even with a change in the d.c. control voltage supplied to the resonance circuit, to improve the reliability and performance of the circuit.