An Integrated Low-Voltage Class AB CMOS OTA

Ramesh Harjani, Randy Heineke, Feng Wang

Research output: Contribution to journalArticlepeer-review

46 Scopus citations


We present a new circuit topology for a low-voltage class AB amplifier. The circuit shows superior current efficiency in the use of the supply current to charge and discharge the output load. It uses negative feedback rather than component matching to optimize current efficiency and performance, resulting in a current boost ratio exactly equal to one. Measurement results for an example circuit fabricated in a 2-μm CMOS process are given. The circuit uses a quiescent supply current of 0.2 μA and is able to settle to a 1% error in 1.1 ms for a 0.4-V input step and a load capacitance of 35 pF. The circuit design is straightforward and modular, and the core circuit can be used to replace the differential pair of other op-amp topologies.

Original languageEnglish (US)
Pages (from-to)134-141
Number of pages8
JournalIEEE Journal of Solid-State Circuits
Issue number2
StatePublished - 1999


  • CMOS operational transconductance amplifier (OTA)
  • Class AB
  • Current utilization
  • Low voltage


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