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Field Effect Transistor Protect Circuit

IP.com Disclosure Number: IPCOM000081094D
Original Publication Date: 1974-Apr-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 21K

Publishing Venue

IBM

Related People

Delecki, JJ: AUTHOR

Abstract

A high-voltage field-effect transistor (FET) driver circuit especially useful with metal insulator oxide semiconductor nonvolatile devices is described. With such nonvolatile devices a 25 to 40 volt range is needed to write and erase the devices. These voltages are beyond the gated breakdown voltage of most FET devices. Although the gate voltage can be increased by process changes, undesirable side effects can occur.

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Field Effect Transistor Protect Circuit

A high-voltage field-effect transistor (FET) driver circuit especially useful with metal insulator oxide semiconductor nonvolatile devices is described. With such nonvolatile devices a 25 to 40 volt range is needed to write and erase the devices. These voltages are beyond the gated breakdown voltage of most FET devices. Although the gate voltage can be increased by process changes, undesirable side effects can occur.

This described arrangement avoids these undesirable side effects, yet increases the voltages to a level such that the breakdown voltage of the devices in the series is not exceeded. The circuit comprises two transistors T1 and T2 connected between a Bvoltage supply and ground. An input signal is applied to the gates of both transistors T1 and T2 and the output is taken at the source of transistor T1. The transistor T1 is formed in a separate isolation pocket 10 which is connected by lead 11 to the source of transistor T2. The substrate of transistor T2 is held at zero volts by lead 12.

When the devices are turned on by a suitable input signal applied to their gates, the node 13 between transistor T1 and T2 is brought to ground. This causes the substrate of transistor T1 to also be brought to ground. When no input signal is received, the transistor T2 is turned off and its source rises such that the drain of T1 is now sustaining the Bvoltage. If the drain to isolation pocket junction of transistor T1 does breakd...