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Supply Voltage and Temperature-Compensation Circuit for Relaxation Type Current Controlled Oscillators

IP.com Disclosure Number: IPCOM000121481D
Original Publication Date: 1991-Sep-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 2 page(s) / 75K

Publishing Venue

IBM

Related People

Soyuer, M: AUTHOR

Abstract

Disclosed is a supply voltage and temperature-compensation circuit for relaxation-type monolithic current-controlled oscillators in digital silicon bipolar technology. This circuit minimizes the dependency of the oscillator center frequency on supply and temperature.

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This is the abbreviated version, containing approximately 52% of the total text.

Supply Voltage and Temperature-Compensation Circuit for Relaxation
Type Current Controlled Oscillators

      Disclosed is a supply voltage and
temperature-compensation circuit for relaxation-type monolithic
current-controlled oscillators in digital silicon bipolar technology.
This circuit minimizes the dependency of the oscillator center
frequency on supply and temperature.

      Relaxation oscillators are widely used in communication
circuits such as phase-locked loops.  One disadvantage common to all
relaxation oscillators is their strong dependence on supply and
temperature fluctuations.  One approach to stabilize them is to use a
second oscillator with a crystal control.  However, this method
requires complex circuitry and has limited applications, especially
at very high frequencies.  Another approach which will be discussed
below is to use the voltage-to-current converter stage preceding the
current-controlled oscillator for compensation purposes.  Since this
stage is always required to make a voltage-controlled oscillator from
a current-controlled oscillator, no extra circuitry is involved.  Due
to its simplicity, this method also lends itself easily to
high-frequency applications.

      The relaxation oscillator with the voltage to current converter
is shown in the figure.  It is well-known that the center frequency
of the oscillator is given by:
                  I
      FCENTER = ___CON____ (1)
                 4VBECT
where VBE is the emitter-base voltage drop of the load diode, and CT
is the timing capacitor.  For the center frequency, the differential
input voltage of the converter stage is zero and therefore:
      ICON =  __1____    (VCC-2VBE-0.5RA  ...