Offset cancelling circuit

Author

Wiegerink, Remco J. ; Seevinck, Evert ; De Jager, Wim

Author_Institution

Fac. of Electr. Eng., Twente Univ., Enschede, Netherlands

Volume

24

Issue

3

fYear

1989

fDate

6/1/1989 12:00:00 AM

Firstpage

651

Lastpage

658

Abstract

A monolithic offset cancelling circuit to reduce the offset voltage at an integrated audio-amplifier output is described. This offset voltage is detected using a low-pass filter with a very large time constant for which only one small on-chip capacitor is needed. The circuit was realized with a bipolar cell-based semicustom array. Measurements have shown that a -3-dB bandwidth below 5 Hz can be realized with a capacitor value of 50 pF. The resulting offset voltage at the audio-amplifier output was 2.5 mV. The offset cancelling circuit increases the wideband noise voltage at the audio-amplifier output by 0.15-MV RMS over the frequency range of 10 Hz to 30 kHz. The use of the offset cancelling circuit eliminates the need for a large external electrolytic capacitor. If an audio amplifier with a single supply voltage is used, a second electrolytic capacitor, needed to obtain a stable reference at half the supply voltage, can be eliminated

Keywords

audio-frequency amplifiers; bipolar integrated circuits; convertors; linear integrated circuits; 10 to 30 kHz; AF amplifier; V/I convertor; bipolar IC; bipolar cell-based semicustom array; integrated audio-amplifier output; low-pass filter; monolithic offset cancelling circuit; offset voltage reduction; wideband noise voltage; Bandwidth; Broadband amplifiers; Capacitors; Circuit noise; Frequency; Integrated circuit measurements; Low pass filters; Noise cancellation; Voltage; Wideband;

fLanguage

English

Journal_Title

Solid-State Circuits, IEEE Journal of

Publisher

ieee

ISSN

0018-9200

Type

jour

DOI

10.1109/4.32022

Filename

32022