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Range Enhancement for Ring Oscillator Delay Element

IP.com Disclosure Number: IPCOM000117687D
Original Publication Date: 1996-May-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 4 page(s) / 70K

Publishing Venue

IBM

Related People

Emeigh, RD: AUTHOR [+3]

Abstract

Disclosed is a method of enhancing a ring oscillator delay element for better range and noise immunity. Optimum delay element range and noise immunity are achieved by making the delayed waveform rise time resemble the input wave form rise time. This is done by lowering the gain of the amplifiers in the delayed waveform circuit.

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Range Enhancement for Ring Oscillator Delay Element

      Disclosed is a method of enhancing a ring oscillator delay
element for better range and noise immunity.  Optimum delay element
range and noise immunity are achieved by making the delayed waveform
rise time resemble the input wave form rise time.  This is done by
lowering the gain of the amplifiers in the delayed waveform circuit.

      In the ring oscillator Voltage Controlled Oscillator (VCO)
shown in Fig. 1, the ability of each delay element to produce the
widest range of delay is essential.  Each delay element should have a
large frequency range for Phase Locked Loop (PLL) applications.

      The delay element needs to have the delayed version of the
input wave form look as near as possible to the input wave form in
terms of rise time.  If this is not the case, then the delay range of
each element will be limited.  Previously designed delay elements
utilize amplifiers that are high gain circuits that tend to square up
the delayed signal.  This tends to make the delay range smaller.

      In the circuit shown in Fig. 2, the two delay element
amplifiers have gains that are reduced.  This slows down the rise
time of the delayed input signal at position 2 in Fig. 2.  This gain
reduction is accomplished by the insertion of resistors, R14 and R15,
at positions 3 and 4 of Fig. 2.  The summed signal at the collectors
of the circuits at positions 1 and 2 of Fig. 2 has a larger range.
The output...