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Voltage Controlled Oscillator

IP.com Disclosure Number: IPCOM000073573D
Original Publication Date: 1971-Jan-01
Included in the Prior Art Database: 2005-Feb-22
Document File: 2 page(s) / 51K

Publishing Venue

IBM

Related People

Cox, DF: AUTHOR

Abstract

This voltage-controlled oscillator provides an output signal having a constant amplitude and duty cycle wherein the oscillator frequency is controlled by voltages VA and VB through high-impedance junctions so as not to affect the amplitude or symmetry of the output waveform. In operation, at time t = 0 with Q1 being switched off and Q2 on, currents I1 and I2 will both flow through Q2 so that output voltage E = +V-R2(I1+I2) and output voltage E = +V. In this condition, the voltage at the base of Q2 equals V minus the voltage drops across the base-emitter junction of transistor Q5 and the zener diode, and the voltage at the base of Q1 is equal to the voltage E minus the voltage drops across the base emitter junction of transistor Q6 and the zener diode.

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Voltage Controlled Oscillator

This voltage-controlled oscillator provides an output signal having a constant amplitude and duty cycle wherein the oscillator frequency is controlled by voltages VA and VB through high-impedance junctions so as not to affect the amplitude or symmetry of the output waveform. In operation, at time t = 0 with Q1 being switched off and Q2 on, currents I1 and I2 will both flow through Q2 so that output voltage E = +V-R2(I1+I2) and output voltage E = +V. In this condition, the voltage at the base of Q2 equals V minus the voltage drops across the base- emitter junction of transistor Q5 and the zener diode, and the voltage at the base of Q1 is equal to the voltage E minus the voltage drops across the base emitter junction of transistor Q6 and the zener diode. Since Q1 is switched off, the base- emitter junction of Q1 is reverse biased so that V1 decreases linearly with respect to time as CT is discharged by the current I1 and V2 is clamped to a constant voltage. V1 decreases until the base-emitter junction of Q1 becomes forward biased. As Q1 turns on its collector voltage drops which drop is coupled to the base of Q2, thereby turning Q2 off, whereby output voltage E jumps to V and the base-voltage of Q1 increases a like amount due to the coupling therebetween. The increase in V1 follows the increase in VB1 which is, in turn , coupled through CT to V2 causing it to increase an equal amount since the switching rate of the transistors is much...