文档介绍：IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 34, NO. 3, MARCH 1999 415
Brief Papers
A Fully Integrated, Untrimmed CMOS
Instrumentation Amplifier with Submicrovolt Offset
Christian Menolfi and Qiuting Huang
Abstract— A low-noise CMOS instrumentation amplifier in- power-supply rejection ratio (PSRR) are required in order to
tended for low-frequency thermoelectric microsensor applications amplify the weak signal without additional interference from
is presented that achieves submicrovolt offset and noise. Key to mon-mode or power-supply variations.
performance is the chopper modulation bined with
a bandpass filter and a matching on-chip oscillator. No external For many decades, the chopper modulation [4]–[10] has
components or trimming are required. The achievable offset been known as an efficient technique to achieve excellent low-
performance depends on the bandpass filter and the oscillator- frequency noise and offset performance and to circumvent the
to-bandpass filter matching accuracy. Constraints are derived for need for trimming. To reach high gain without being saturated
an optimum and a given matching accuracy. The improvement by the original offset, the amplifier between the chopping
mon-mode rejection ratio (CMRR) in chopper amplifiers
is discussed. The amplifier features a total gain of 77 modulator and demodulator is usually an ac amplifier. If
dB