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FET Input Circuit

IP.com Disclosure Number: IPCOM000074856D
Original Publication Date: 1971-Jun-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 22K

Publishing Venue

IBM

Related People

Palfi, TL: AUTHOR

Abstract

Bipolar circuits can be coupled to an FET circuit and the threshold voltage of the FET device can be reduced. This occurs when the source electrode of the FET device is used as an input terminal rather than the gate electrode. Use of the source electrode as the input terminal also increases the gain of the FET devices as well as reducing the gate electrode shorts due to static charges.

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FET Input Circuit

Bipolar circuits can be coupled to an FET circuit and the threshold voltage of the FET device can be reduced. This occurs when the source electrode of the FET device is used as an input terminal rather than the gate electrode. Use of the source electrode as the input terminal also increases the gain of the FET devices as well as reducing the gate electrode shorts due to static charges.

Bipolar input circuit 10 is coupled to FET circuit 12 via connection 14. Circuit 12 comprises FET devices 16 and 18. The input from circuit 10 is applied to source electrode S of device 16. Gate electrode G is connected to a source of fixed potential. Drain electrode D is connected to the output terminal. Device 18 has gate and drain electrodes connected to a fixed potential higher than that of device 16 and a source electrode connected to the output terminal.

When the source electrode of device 16 is employed as the input circuit, the threshold voltage is reduced as a function over the substrate voltage because of the inherent characteristic of the device. The gain of the device is also increased because the drain current versus source voltage characteristic has greater slope than for the case where the gate terminal is the input electrode. Due to the increased gain, the circuit can generate large output signals with smaller input signals so that the driver circuit power can be kept at a minimum.

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