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Floating Power Supply for Sampling Switch

IP.com Disclosure Number: IPCOM000096068D
Original Publication Date: 1964-Nov-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Faber, U: AUTHOR

Abstract

This is a sampling switch which is energized by a floating power supply, eliminating requirements for ground isolation devices such as transformers.

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Floating Power Supply for Sampling Switch

This is a sampling switch which is energized by a floating power supply, eliminating requirements for ground isolation devices such as transformers.

Transistors 10 and 12 in combination with resistors 14 and 16 constitute a switch or chopper of the Bright type. Switching is accomplished by the application of an appropriate potential between nodes C and D. Sufficient base current in transistors 10 and 12 causes the impedance between input and output terminals A and B to be reduced, thus placing switch 1 in the on state. Removal of the base current results in an increase in the impedance, placing switch 1 in its off state.

In order to avoid introducing inaccuracies into the voltage being sampled, it is necessary that the switch be isolated or floating with respect to ground. This is accomplished by the use of a pair of insulate gate field effect transistors, of which transistors 18 and 20 are representative, and a floating switching power supply
22. The conductive condition of each field effect transistor is controlled by the potential applied to its respective gate electrodes, i. e., 24 and 26 via control inputs 30, 32, etc.

The characteristic large DC resistance which exists between the gate electrodes and the semiconductor bodies of the field effect transistors provides the desired isolation between the control input and the Bright switches. This, therefore, permits application of control signals to the field effect tran...