VOLTAGE CONTROLLED OSCILLATOR

PURPOSE:To set a capacitance of a capacitor so as not to be affected by parasitic capacitance or stray capacitance of circuit components by deciding a constant current source deciding an oscillating frequency and a current source deciding control sensitivity. CONSTITUTION:Third and fourth transistors(TRs) 3, 4 act like a constant current source in which a constant voltage is applied to their bases to cause a prescribed current to flow thereby deciding an oscillating frequency (f). Moreover, a constant voltage source 25 comprising 7th and 8th TRs 7, 8 to decide its control sensitivity in addition to the former constant current source is connected to each emitter of 1st and 2nd TRs 1, 2, the emitters of the 7th and 8th TRs connect respectively to ground via 2nd resistors 18, 19, and bases of the 7th and 8th TRs are connected to a control input terminal 21. A control voltage Vc is given to the control input terminal 21 to vary the frequency. In this case, a larger capacitance is selected for a capacitor 9 and a resistance RE1 of the 1st resistors 14, 15 is selected smaller or a voltage of a constant voltage source 25 is set higher to oscillate a higher frequency.