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Bipolar IC Voltage Extender

IP.com Disclosure Number: IPCOM000042986D
Original Publication Date: 1984-Jun-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Hedman, RL: AUTHOR

Abstract

Bipolar integrated circuits (ICs) require bias voltages on certain diffusions to properly isolate the circuit components from each other. Typically, the most negative voltage applied to the bipolar IC is connected to the P-type substrate. Therefore, all N-type devices diffused into the substrate (Fig. 1) are necessarily at an equal or higher voltage, which provides the necessary isolation for the individual transistors. Resistors are isolated in a similar fashion. This arrangement, however, has a limit on how large the voltage difference may be across this P-N junction. This limit is called the EPI to isolation breakdown voltage. Heretofore, this EPI to isolation voltage limit was used as a limit to the difference between the most positive and the most negative voltage a bipolar integrated circuit might use, i.e.

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Bipolar IC Voltage Extender

Bipolar integrated circuits (ICs) require bias voltages on certain diffusions to properly isolate the circuit components from each other. Typically, the most negative voltage applied to the bipolar IC is connected to the P-type substrate. Therefore, all N-type devices diffused into the substrate (Fig. 1) are necessarily at an equal or higher voltage, which provides the necessary isolation for the individual transistors. Resistors are isolated in a similar fashion. This arrangement, however, has a limit on how large the voltage difference may be across this P-N junction. This limit is called the EPI to isolation breakdown voltage. Heretofore, this EPI to isolation voltage limit was used as a limit to the difference between the most positive and the most negative voltage a bipolar integrated circuit might use, i.e., the maximum supply voltage used to power a circuit. In order to extend the maximum supply voltage for a given bipolar IC technology, a reverse biased NPN transistor base emitter junction is used in series with any circuit connection to the most positive voltage which the circuit requires. Schematically, this is shown in Fig. 2. The magnitude of the extension is the voltage dropped across the emitter-base junction, typically referred to as the Zener voltage.

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