Browse Prior Art Database

MOSFET Substrate Self Biasing

IP.com Disclosure Number: IPCOM000073718D
Original Publication Date: 1971-Jan-01
Included in the Prior Art Database: 2005-Feb-22
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Frantz, H: AUTHOR [+2]

Abstract

This multivibrator can be fabricated on a monolithic chip and used to generate the substrate voltage for the chip, since the multivibrator oscillates without a substrate bias.

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MOSFET Substrate Self Biasing

This multivibrator can be fabricated on a monolithic chip and used to generate the substrate voltage for the chip, since the multivibrator oscillates without a substrate bias.

The March 1969 issue of the IBM Technical Disclosure Bulletin on page 1219 describes a circuit which, when supplied with input pulses, will generate substrate bias for the monolithic chip on which it is fabricated. This astable multivibrator can be used to supply the input to that circuit. The astable multivibrator consists of a frequency determining network, biasing network and a circuit to insure a loop voltage gain of greater than one for unconditional oscillation. The frequency determining network consists of first capacitor C1 in series with the equivalent resistance of device Q6 and a second capacitor C2 in series with device Q5. Because of the size limitation of capacitors C1 and C2 for area and power dissipation reasons, equivalent resistance of devices Q5 and Q6 is made relatively high to achieve the long time constants required. This high resistance of devices Q5 and Q6 is achieved by biasing these devices close to their threshold voltages using a biasing network consisting of devices Q1 and Q2. Devices Q3 and Q4 insure that under no circumstances are devices Q7 and Q8 off at the same time thereby causing the AC loop gain to be less than one. Once oscillation has been initiated, either device Q3 or Q4 is on and the source of device Q2 is virtually at...