Browse Prior Art Database

Dynamic Substrate Bias to Achieve Radiation Hardening

IP.com Disclosure Number: IPCOM000045667D
Original Publication Date: 1983-Apr-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

DeBar, DE: AUTHOR

Abstract

A substrate bias compensation circuit is disclosed which monitors the threshold voltage of a sample FET circuit on an integrated circuit chip and modifies the substrate voltage for the chip to compensate for variations in the monitor threshold voltage due to radiation damage such as might occur in a space satellite exposed to a solar flare.

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Dynamic Substrate Bias to Achieve Radiation Hardening

A substrate bias compensation circuit is disclosed which monitors the threshold voltage of a sample FET circuit on an integrated circuit chip and modifies the substrate voltage for the chip to compensate for variations in the monitor threshold voltage due to radiation damage such as might occur in a space satellite exposed to a solar flare.

In the figure, R1 and R2 comprise a voltage divider to establish a voltage Vt which is chosen to be representative of a typical threshold voltage for the device in the integrated circuit (IC) being used. R4 and R5 comprise a voltage divider to establish a voltage reference Vr. Operational amplifier A1 will force the substrate of Ql to whatever voltage is needed to assure that Vr'=Vr. Vr and R3 are chosen to assure a typical in for the selected Vt in Q1. When gamma rays or other radiation pass through the sensing FET Q1, the intrinsic threshld voltage of Q1 will go lower. Since Vt is held fixed by R1 and R2, Q1 will tend to conduct more heavily, this will in turn tend to lower Vr. Since Vr is fed back to the non- inverting input of Al, the output of A1 (Vsx) will move more negative, to a voltage such that Vr'=Vr and the intrinsic threshold voltage equals Vt for ID.

The output of the amplifier, Vsx, also provides substrate back bias for the MOS IC. Because Q1 is chosen to be a representative device of the same process used by the MOS IC, any changes in Vt due to gamma radiati...