Browse Prior Art Database

Fast Bipolar Analog Switch Circuit

IP.com Disclosure Number: IPCOM000039081D
Original Publication Date: 1987-Apr-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 42K

Publishing Venue

IBM

Related People

Ebler, MB: AUTHOR [+2]

Abstract

Switch circuit A illustrates an analog switch technique for bipolar integrated circuits useful for switching low impedance sources in times as small as nanoseconds, and worst-case offsets less than millivolts. Circuit A is both temperature and beta compensated, has TTL (transistor-transistor logic) compatible inputs, and can operate over a wide range of power supplies including ground up as well as +/- voltages. Transistor T10 generates a current of value '2I' which can then be selected by twin tailed pair T11 and T12 to activate current mirror T1 and T2. This current is presented to node '1' and splits equally between diodes D11 and D12. Transistor T9 generates a current of value 'I' which passes through diode D12, thus guaranteeing this equal split at '1'.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 80% of the total text.

Page 1 of 2

Fast Bipolar Analog Switch Circuit

Switch circuit A illustrates an analog switch technique for bipolar integrated circuits useful for switching low impedance sources in times as small as nanoseconds, and worst-case offsets less than millivolts. Circuit A is both temperature and beta compensated, has TTL (transistor-transistor logic) compatible inputs, and can operate over a wide range of power supplies including ground up as well as +/- voltages. Transistor T10 generates a current of value '2I' which can then be selected by twin tailed pair T11 and T12 to activate current mirror T1 and T2. This current is presented to node '1' and splits equally between diodes D11 and D12. Transistor T9 generates a current of value 'I' which passes through diode D12, thus guaranteeing this equal split at '1'. T7 is used to beta compensate the losses of the lateral PNP transistors that occur in T12. Diodes D11 and D12 are a matched pair with equal currents. Diode D13 and transistor T5 are area ratioed by four to produce equal tracking at four times the current. This is necessary to provide adequate output drive from switch circuit A. T3, T4, T6, and T8 generate the bias current necessary for the output device T5. The number of switch inputs can be extended to "n" (an indefinite number) by merely repeating the selector stage and the diodes, as illustrated in the figure. The illustrated circuit includes a selector stage between the reference lines a-a and b-b, and for this purpose o...