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Linear Junction Capacitor

IP.com Disclosure Number: IPCOM000084054D
Original Publication Date: 1975-Sep-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Gersbach, JE: AUTHOR

Abstract

Linear junction capacitors can be comprised of two back-to-back diodes driven at low voltages, such that each acts as a capacitor and provides a reduced junction capacitance variation.

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Linear Junction Capacitor

Linear junction capacitors can be comprised of two back-to-back diodes driven at low voltages, such that each acts as a capacitor and provides a reduced junction capacitance variation.

In integrated circuits it is frequently desirable to use junctions as capacitors for time delays in generating exponential waveforms. A major problem with this type of capacitor is it is voltage dependent.

Described is a method of reducing the effective voltage bias on capacitance which is a function of the cube root of voltage. This cube root dependence can be reduced by using two junctions in parallel and connected in opposing polarities.

Since the junctions are connected in opposing polarities, the capacitance of one will increase as the other decreases, providing compensation. For example, if a voltage range of + or - 0.4 volt is considered the change in capacitance over this range is + or - 3%. If a single diode were used under the same conditions, the change in capacitance over this same range of voltage would be + or - 18%.

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