A Low-Leakage Body-Guarded Analog Switch in 0.35- \mu\mbox BiCMOS and Its Applications in Low-Speed Switched-Capacitor Circuits

A low-leakage body-guarded analog switch (BGswitch) for slow switched-capacitor (SC) circuits is presented. The improvement of accuracy in SC circuits employing BG-switches is demonstrated by comparing their performance with counterparts employing conventionally biased CMOS switches in three applications: sample-and-hold (S/H) amplifier, SC amplifier, and highvoltage drain-extended MOSFET (DEMOS). The leakage currents of BG-switch-enabled circuits are characterized across process variations and different operation voltages in all demonstrated applications. With nominal output voltages at room temperature, the average absolute leakage current of BG-switch-enabled S/H amplifier (12.02 aA), SC amplifier (54.52 aA), and DEMOS (53.71 fA) show leakage current improvement of 21, 28, and 17 dB, respectively, compared with equivalent circuits utilizing transmission gates (TGs). BG-switch-enabled S/H circuits and SC amplifiers with average performance exhibit lower leakage currents up to 100 °C compared with TG-enabled circuits. The demonstrated applications utilizing BG-switches were fabricated in a standard 0.35-μm BiCMOS process.