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Voltage Controlled Oscillator

IP.com Disclosure Number: IPCOM000087796D
Original Publication Date: 1977-Mar-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Newman, EL: AUTHOR

Abstract

A voltage-controlled oscillator is described having a center frequency independent of temperature, high impedance voltage control and center frequency set up without change of phase gain. The gain in the phase-locked loop is independent of any fine frequency adjustment.

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Voltage Controlled Oscillator

A voltage-controlled oscillator is described having a center frequency independent of temperature, high impedance voltage control and center frequency set up without change of phase gain. The gain in the phase-locked loop is independent of any fine frequency adjustment.

The circuit diagram shows a square-wave oscillator whose frequency is controlled by the voltage Vin applied to the input terminal. Starting with T1 on, current from T9 and T10 flows through T1 and T3. The emitter of T3 provides a reference voltage of approximately 1.2 volts. This voltage is emitter-followed by T5 and drops a further VBE via diode T8 and thus holds T2 off until capacitor C has charged to 1.2 volts by T10 collector current. Then T2 starts to turn on, and feedback causes the oscillator to switch to the opposite state. Diodes T7 and T8 prevent saturation of T1 and T2. T11 and T12 are equal current sources for T6, T7 and T7, T8.

The output from the oscillator can be taken from any convenient point, for example, an emitter follower from any of the emitters of T3, T4, T5, T6, T7 or T8.

The reference voltage at T3 or T4 emitter is the band gap of silicon which is independent of temperature. By running T13 (also T14, T15) at different emitter current densities to T9 and T10, a Delta VBE is created. This Delta VBE has a positive temperature coefficient which is multiplied by RL13 to compensate for the negative temperature coefficient of T3 or T4. RE13

The contr...