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Transistor Switch

IP.com Disclosure Number: IPCOM000096505D
Original Publication Date: 1963-Jun-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 21K

Publishing Venue

IBM

Related People

Painke, H: AUTHOR [+2]

Abstract

If the flow of current through an inductance is abruptly terminated by a transistor switch, the cutoff voltage occurring at the inductance can destroy the transistor. That danger can be avoided if the transistor is not rendered completely nonconductive immediately on cutoff. Thus at first, a current limiting the cutoff voltage to a permissible level still flows through the inductance.

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Transistor Switch

If the flow of current through an inductance is abruptly terminated by a transistor switch, the cutoff voltage occurring at the inductance can destroy the transistor. That danger can be avoided if the transistor is not rendered completely nonconductive immediately on cutoff. Thus at first, a current limiting the cutoff voltage to a permissible level still flows through the inductance.

Assume transistor 1 initially is in conductive condition. The operating circuit includes the inductance 2 to be switched. It is now supplied through an amplifier 4 with a control pulse rendering it completely nonconductive. The cutoff voltage builds up at inductance 2. In order to limit this cutoff voltage, at least part is supplied through a negative feedback channel 3 and amplifier 4 to transistor 1. This control voltage keeps it conductive to the required extent. The energy stored in inductance 2 decreases, so that after a given time the negative feedback action stops and transistor 1 is cut off entirely.

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