A Chopper-Stabilized Amplifier with a Relaxed Fill-In Technique and 22.6pA Input Current

Thije Rooijers*, Johan H.H. Huijsing, Kofi A.A. Makinwa

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

2 Citations (Scopus)
166 Downloads (Pure)

Abstract

In chopper amplifiers, the interaction between the input signal and the chopper clock can cause intermodulation distortion (IMD). This is mainly due to finite amplifier bandwidth, which causes signal-dependent output spikes at the chopping transitions. Such chopper-induced IMD can be mitigated by the fill-in technique, which involves ping-ponging between the outputs of two identical OTAs chopped in quadrature, thus generating a spike-free output. In this letter, a relaxed implementation is proposed in which the output of a fill-in OTA is only briefly used to avoid the spikes of a chopped main OTA. As a result, the fill-in OTA does not need to be chopped, and so it can be duty-cycled to save power. Furthermore, the chopper ripple caused by the main OTA can now be suppressed by a single low-noise ripple-reduction loop, rather than the two AZ loops required in a previous ping-pong implementation of the fill-in technique. Compared to the latter, the proposed amplifier achieves similar IMD performance (-125.7 dB), a 25× lower input current (22.6 pA), and a flat noise floor (12 nV/ Hz).

Original languageEnglish
Pages (from-to)165 - 168
Number of pages4
JournalIEEE Solid-State Circuits Letters
Volume6
DOIs
Publication statusPublished - 2023

Bibliographical note

Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care
Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.

Keywords

  • Choppers (circuits)
  • duty-cycled OTA
  • intermodulation distortion (IMD)
  • relaxed fill-in technique

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