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Additional Capacitor to Reduce the Rate Effect Sensitivity in a Thyristor Crosspoint

IP.com Disclosure Number: IPCOM000052362D
Original Publication Date: 1981-Jun-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Benichou, C: AUTHOR [+3]

Abstract

A first solution to this problem was published in the IBM Technical Disclosure Bulletin 21, 1080-1081 (August 1978). It was there recommended to place a capacitor C between the Rate and the cathode of the thyristor.

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Additional Capacitor to Reduce the Rate Effect Sensitivity in a Thyristor Crosspoint

A first solution to this problem was published in the IBM Technical Disclosure Bulletin 21, 1080-1081 (August 1978). It was there recommended to place a capacitor C between the Rate and the cathode of the thyristor.

Unfortunately, the proposed diffused capacitor design introduces a capacitance between the N/+/ electrode (tied to the thyristor gate) and the common substrate of the chip (in general connected to ground; see Figs. 1 and 2 of the above-cited publication).

As a matter of fact, the rate effect sensitivity is different if triggering is caused by an upgoing voltage transient on the anode or by a downgoing voltage transient on the cathode. Both cases appear with different amplitudes and transition times in a space division network.

The capacitance between the gate and the substrate improves rate effect immunity for upgoing transients on the anode because it reduces the current flowing through R(GK) (see Fig. 2 of the above-cited publication. However it decreases the rate effect immunity of downgoing transients on the cathode, since the discharging current flows through R(GK), thereby increasing the gate- cathode voltage.

Starting from this solution, a composite structure is now proposed which should be adjusted to provide the required compromise between anode and cathode sensitivity.

In general, the cathode-to-gate capacitance has to be as high as possible, while the gate-...