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Linear Nonlinear Variably Sensitive Voltage Controlled Oscillator

IP.com Disclosure Number: IPCOM000081296D
Original Publication Date: 1974-May-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 3 page(s) / 54K

Publishing Venue

IBM

Related People

Beavers, JA: AUTHOR [+2]

Abstract

A 135 KHz voltage-controlled oscillator is shown, in which the output frequency responds linearly with positive or negative variations in control voltage. Although this circuit was designed for a particular application, the configuration lends itself to a variety of performance alternatives. For example, by changing the values of a few key resistors, the oscillator can be tailored to a desired frequency, symmetry or control-voltage sensitivity. Also, temperature dependence is relatively easy to define, since the sensitivity to this parameter is proportional to the temperature coefficient of the resistors.

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Linear Nonlinear Variably Sensitive Voltage Controlled Oscillator

A 135 KHz voltage-controlled oscillator is shown, in which the output frequency responds linearly with positive or negative variations in control voltage. Although this circuit was designed for a particular application, the configuration lends itself to a variety of performance alternatives. For example, by changing the values of a few key resistors, the oscillator can be tailored to a desired frequency, symmetry or control-voltage sensitivity. Also, temperature dependence is relatively easy to define, since the sensitivity to this parameter is proportional to the temperature coefficient of the resistors.

The oscillator utilizes two power supplies, one for providing an accurate voltage reference and one for controlling the frequency. A potentiometer, R8, is furnished for adjustment of the oscillator frequency to 135 KHz with the controlling voltage at 24.0 volts and ambient temperature of 25 degrees C. All reference voltage levels are derived from the 6 volt zener diode, D1. These voltages control the charging current of capacitor C6 through R7, and control the discharging current of capacitor C6 through resistors R8 and R9. The current through resistor R7 is calibrated to be half that of the current through R8 and R9. The charge and discharge current of C6, therefore, is equal.

Other reference levels derived from zener D1 are the charging voltage limits of capacitor C6 set by divider R14, R15, and R16, and the operational voltage levels for current switches T2-T3 and T5-T6 set by divider R10, R11, R12, and R13.

The resistors R2 and R3 allow current from separate voltage sources (+6v and +24V) in such a way as to fragmentize any voltage change effects of the +24.0 volt supply on the voltage drops of R4, R5, and R6. In this case, the change in voltage drop of R4, R5, and R6 are calibrated to be a portion of the change in the +24.0 volt supply from a supply change of -10% to +10%. Any change in the voltage drops of R4, R5, and R6 affect the oscillator frequency proportionally.

The key to the oscillator's operation is the constant-current charge and discharge of capacitor C6. The equ...