An instrumentation amplifier (IA) with continuous tuning of the voltage gain, suitable for operation over a wide frequency range, and aimed to electrical bioimpedance spectroscopy, is proposed. The operation principle… Click to show full abstract
An instrumentation amplifier (IA) with continuous tuning of the voltage gain, suitable for operation over a wide frequency range, and aimed to electrical bioimpedance spectroscopy, is proposed. The operation principle of the IA is based on indirect current feedback (ICF), which leads to an almost-constant bandwidth regardless of the value of the programmed voltage gain. The use of improved voltage followers in the transconductors required in the ICF technique allows achieving a compact implementation with a bandwidth compatible with bioimpedance spectroscopy applications. The tuning strategy relies on a continuously programmable current mirror that can be electronically adjusted by means of a control current. The IA has been designed and fabricated in 180 nm CMOS technology to operate with a 1.8-V single supply. The experimental characterization of the silicon prototypes showed a gain programmability range higher than 45 dB, between −4.6 dB and 41.2 dB, a BW around 3 MHz, and a maximum CMRR at DC higher than 86 dB, all this with a minimum current consumption of $144.8~\mu \text{A}$ and an area occupation of 0.0196 mm2.
               
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