Low-Voltage CMOS Bulk-Driven Indirect Current Feedback Instrumentation Amplifier

A CMOS bulk-driven instrumentation amplifier (IA) suitable for operation under low supply voltage conditions, is presented in this paper. The principle of operation of the proposed IA is based on indirect current feedback (ICF). The use of bulk-driven transistors in the input and the output transconductor of the ICF structure, allows acquiring signals superimposed to a DC level around midsupply in very low supply environments. A prototype has been fabricated in standard $0.35- \mu \mathrm{m}$ CMOS technology to operate with a 1-V supply voltage. The experimental results showed the capability of the IA to handle signals around a DC level of 0.5 V with an effective input resistance in the $\mathrm{G}\Omega$ range, a bandwidth of 115 kHz, and a THD below −40 dB for output signals up to $480\ \text{mV}_{pp}$ when programmed with a voltage gain equal to 2 V/V.