In mixed level applications, accurate voltage references are difficult
to realise due to the lack of lateral pnps and the large offsets inhe
rent to CMOS opamps. If low power is essential, the accuracy is mainly
impaired by the increased offset of the opamps. It is shown that by u
sing chopping techniques, the accuracy of a bandgap voltage reference
can be improved by about ten times without laser trimming, with the ad
ded benefit of reducing the 1/f noise of the amplifier.