Browse Prior Art Database

Voltage Controlled Oscillator with Temperature, Power Supply and Process Compensations

IP.com Disclosure Number: IPCOM000109622D
Original Publication Date: 1992-Sep-01
Included in the Prior Art Database: 2005-Mar-24
Document File: 2 page(s) / 106K

Publishing Venue

IBM

Related People

Mollier, P: AUTHOR [+2]

Abstract

A Voltage Controlled Oscillator (VCO) is described that contains compensation techniques which stabilize the circuit against temperature, power supply and process variations.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Voltage Controlled Oscillator with Temperature, Power Supply and Process Compensations

       A Voltage Controlled Oscillator (VCO) is described that
contains compensation techniques which stabilize the circuit against
temperature, power supply and process variations.

      The circuit schematic is shown in the figure.  Its operation is
based on a relaxation oscillator made of two cross-coupled inverters
with capacitive coupling between emitters.  Compensation techniques
are applied to the current sinking circuitry that controls its
oscillating frequency.

      In order to reduce power dissipation, only one emitter-follower
buffer per output is used.  Saturation of transistors T1 and T2 is
avoided by two clamp diodes DO and DI connected to VCC and by a
common load resistor RSHI that keeps the Up level of the base voltage
at a level lower than VCC.  The RSHI/RI (=RSHI/RO) ratio can be
adjusted to get the desired signal amplitude, let us say around 500
mV.  The emitter coupling capacitor CE being large enough to be
dominant compared with the stray capacitors of the circuit, the
oscillating frequency is mostly controlled by CE and by the DC
current sunk by transistors TE1 and TE2 at nodes E1 and E2,
respectively.  At this level, the circuit is actually a Current
Controlled Oscillator.  The Voltage to Current conversion is done by
a conventional current mirror (current through TRF mirrored into TE1
and TE2) fed by a control circuit compensated against temperature,
power supply and process variations.

      This control circuit is a two-input stage made of two emitter
followers TINA-TINB that drive current into diodes TRF and TVTC1
through resistors RRA and RRB, respectively.  This circuit is made
differential by using an inverter transistor TVTC2 that mirror...