Original Publication Date: 1991-Mar-01
Included in the Prior Art Database: 2005-Apr-02
Chappell, BA: AUTHOR [+3]
Disclosed is a Voltage Controlled Oscillator that uses N and P pass gates between the oscillator stages for wide frequency tunability. The oscillator is turned off and on by means of an externally applied signal to one of the oscillator stages.
a Voltage Controlled Oscillator that uses N
and P pass gates between the oscillator stages for wide frequency
tunability. The oscillator is turned off and on by means of an
externally applied signal to one of the oscillator stages.
diagram of the voltage-controlled oscillator is shown
in Fig. 1. A key feature is the N and P devices inserted between the
various stages of the ring oscillator. By changing the voltage on the
gates of these devices (PDEV and NDEV) the resistance between each
stage of the ring oscillator, and therefore the time constant, can be
changed. Oscillator waveforms are shown in Fig. 2. The variation in
cycle time with PDEV and NDEV gate voltages is shown in Fig. 3. As
the voltage on these devices is reduced, the cycle time will increase
from the fully on N and P device case to the case where these devices
are off and the oscillator stops cycling. The parallel combination
of an N and P device makes a full voltage swing possible at the input
to each stage (node B, D, E) and provides almost a constant
resistance as the node voltage transition for fixed N and P device
gate voltages. Obviously, the cycle time can be further adjusted by
varying the number of stages in the ring oscillator and by adjusting
the size of the parallel N and P devices.
voltage-controlled oscillator is activated by means of the
IN signal shown in the circuit diagram of Fig. 1. The first...