—This paper presents an SOI-CMOS capacitive feedback op-amp for electronic data acquisition system in down-hole-drilling application which operates at high temperature (>170 °C) regime. The op-amp is designed to be two-stages where first stage is folded cascode. A constant-gm bias circuit is adopted to maintain no degradation of the closed loop gain and high cut-off frequency of the op-amp for high temperature application. A commercially available 1 um SOI-CMOS technology was chosen. Measurements from 0 °C to 200 °C shows that trans conductance of the constant-gm bias circuit stays to 50uS within ± 2 % accuracy and the closed-loop ac gain stays to constant value of 19.8 dB (2 % less from 20 dB) for those temperature range. Otherwise high cut-off frequency starts to increase from 240 kHz at 0 °C to 320 kHz at 200 °C.
Index Terms—SOI-CMOS, capacitive feedback, op-amp, high temperature electronics, constant-gm current reference circuit.
The authors are with Institute of Microelectronics, A*STAR (Agency for Science, Technology, and Research), Singapore.
Cite: Jeongwook Koh, M. Annamalai Arasu, and Minkyu Je, "A 20 dB, 200 kHz SOI-CMOS Capacitive Feedback Op-Amp for High Temperature Application," International Journal of Information and Electronics Engineering vol. 3, no. 1, pp. 35-38, 2013.