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Integrated Bipolar Transistor Analog Switch

IP.com Disclosure Number: IPCOM000049576D
Original Publication Date: 1982-Jun-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 20K

Publishing Venue

IBM

Related People

Bersac, JM: AUTHOR [+3]

Abstract

In many applications, it is desirable to have a switch capable of switching an analog signal varying over a symmetrical wide current range. Unfortunately, the well-known integrated single bipolar transistor switch does not have the above capability owing to the presence of a parasitic substrate transistor, unless a large current flow in the substrate is acceptable. The figure illustrates a two bipolar transistor switch which has the desired capability.

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Integrated Bipolar Transistor Analog Switch

In many applications, it is desirable to have a switch capable of switching an analog signal varying over a symmetrical wide current range. Unfortunately, the well-known integrated single bipolar transistor switch does not have the above capability owing to the presence of a parasitic substrate transistor, unless a large current flow in the substrate is acceptable. The figure illustrates a two bipolar transistor switch which has the desired capability.

Referring to the figure, the analog switch is comprised of only two bipolar transistors T1 and T2, the emitter of T1 being connected to the collector of T2, and the emitter of T2 being connected to the collector of T1. Transistors T1 and T2 are simultaneously set ON or OFF by current sources CS1 and CS2, respectively. The interconnection of T1 and T2 compensates for the effects of the parasitic substrate transistors, and the analog switch seen between nodes A and B is fully symmetrical.

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