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Browse Prior Art Database

Sampling Switch

IP.com Disclosure Number: IPCOM000094692D
Original Publication Date: 1965-Apr-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Hosick, WH: AUTHOR

Abstract

The turnoff or recovery time of a sampling switch of the Bright type can be decreased. This is realized by providing a path for the discharge of minority carrier charge after the transistors of the switch are turned off.

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Sampling Switch

The turnoff or recovery time of a sampling switch of the Bright type can be decreased. This is realized by providing a path for the discharge of minority carrier charge after the transistors of the switch are turned off.

In this sampling switch, the operating state of transistors T1 and T2 is controlled by field effect transistor F1. When a positive-going square wave sampling potential Vs is applied to the base of F1, F1 assumes its low impedance state allowing current from floating source Vb to bias T1 and T2 conductive. When Vs terminates, F1 assumes its high impedance state, permitting T1 and T2 to become nonconductive again. However, this return of T1 and T2 to nonconductivity is not immediate. This is because the minority carrier charge stored in T1 and T2 maintains conduction for a period after the termination of Vs.

In order to minimize the length of this period of maintained conductance, field effect transistor F2 is driven into its low impedance state simultaneously with the termination of Vs to rapidly dissipate the minority carrier charge. Normally, F2 remains in its high impedance state to maintain the isolation from ground necessary for accurate sampling. However, when Vs terminates, it causes the inverting and differentiating circuit, comprised of transistor T3, capacitor C, and resistor R, to drive F2 momentarily into its low impedance state with a positive spike pulse. At this time, minority carrier charge stored in T1 and T2 while...