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Schottky Devices in an Analog Process

IP.com Disclosure Number: IPCOM000089549D
Original Publication Date: 1977-Nov-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Bhansali, MM: AUTHOR

Abstract

The high voltage switching circuit of Fig. 1 achieves high switching speed by having a Schottky diode connected in parallel with the base-collector junction to maintain the base-collector diode at less than a full forward bias voltage (off-state), thereby minimizing the charge stored in the junction. However, for high voltage applications (50 V) there is too much resistance for the collector resistance RC1 to maintain the base-collector diode off.

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Schottky Devices in an Analog Process

The high voltage switching circuit of Fig. 1 achieves high switching speed by having a Schottky diode connected in parallel with the base-collector junction to maintain the base-collector diode at less than a full forward bias voltage (off- state), thereby minimizing the charge stored in the junction. However, for high voltage applications (50 V) there is too much resistance for the collector resistance RC1 to maintain the base-collector diode off.

To solve this problem, the magnitude of the resistance Rd, parallel with the base-collector circuit, as shown in the equivalent circuit of Fig. 2, and in series with the Schottky diode, can be adjusted to be approximately one-half of RC1 so as to hold the base-collector junction off. This is accomplished by increasing the effective cross-sectional area of Rd by approximately doubling the area of the Schottky metal contact with respect to the base-emitter area by enlarging the contact area of the Schottky barrier diode.

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