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Resistor in Series With the Contacts to Isolation on Bipolar Chips

IP.com Disclosure Number: IPCOM000080658D
Original Publication Date: 1974-Jan-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Bode, JW: AUTHOR [+2]

Abstract

On bipolar chips, the P isolation must be connected to the most negative voltage, in order to back bias the PN junction formed by the isolation substrate and the N epitaxy. This description proposes inserting a diffused resistor in the path between the voltage supply and the contact to the substrate. See the figure.

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Resistor in Series With the Contacts to Isolation on Bipolar Chips

On bipolar chips, the P isolation must be connected to the most negative voltage, in order to back bias the PN junction formed by the isolation substrate and the N epitaxy. This description proposes inserting a diffused resistor in the path between the voltage supply and the contact to the substrate. See the figure.

This supply-to-junction resistance must be low enough to maintain substrate- to-component reverse bias and prevent noise coupling via the substrate, and also be large enough to prevent excessive currents during certain power-supply failures or sequencing. The first requirement can be met by the conventional method of distributing the substrate contacts uniformly across the chip. However, then the resistance between a substrate contact and components nearby is less than the minimum allowed. Using high-value resistors in each voltage path increases the resistance to an acceptable value.

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