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Browse Prior Art Database

LOW NOISE, LOW POWER VOLTAGE REFERENCE

IP.com Disclosure Number: IPCOM000005809D
Original Publication Date: 1989-Aug-01
Included in the Prior Art Database: 2001-Nov-08
Document File: 2 page(s) / 80K

Publishing Venue

Motorola

Related People

Darrell E. Davis: AUTHOR

Abstract

A five volt band gap voltage reference with improved noise characteristics has been developed. The circuit also avoids the beta dependency problems of past band gap circuits due to use of P channel input devices.

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MOlOROLA Technical Developments Volume 9 August 1969

LOW NOISE, LOW POWER VOLTAGE REFERENCE

by Darrell E. Davis

A five volt band gap voltage reference with improved noise characteristics has been developed. The circuit also avoids the beta dependency problems of past band gap circuits due to use of P channel input devices.

   This circuit uses four closely matched bipolar arrays. QNl, 3,5, 7 are four arrays of eight bipolar devices. Each device in QNI is identical to QN2 and so on for QN 3,5 & 7. These arrays are series connected to form a bandgap reference of nominally 5 volts.

   Previously, five volt references of the bandgap nature were of the single device level with an output voltage of typically 1.2 volts. Using a suitable feedback amplifier with gain resulted in an output voltage that was pro- grammable by varying thegain of the output amplifier.Theoutput noiseof thevoltage regulator was acombina- tion of reference noise multiplied by the gain of the output amplifier and noise due to the resistive feedback network. For lower power operation the resistive feedback network must be on the order of 1OOK ohms to avoid substantial current drain. Resistors with these high values can contribute substantially to the total output noise of the regulator. The higher value of reference voltage that this circuit generates allows the use of a unity gain output amplifier. The contribution of this amplifier then becomes negligible compared with the output noise of the refer...