Reconfigurable Low-Power CMOS Amplifier Stages for Broadband Impedance Spectroscopy

Abstract

In this paper, a fully differential amplifier is proposed in a 1.8 V-0.18 μm CMOS (Complementary Metal-Oxide-Semiconductor) technology, which can accommodate both voltage (V-mode) and current (C-mode) inputs. Post-layout simulation results show a fixed gain amplifier exhibiting a 26 dB (V-mode)/89 dBΩ (C-mode) gain and a programmable gain amplifier featuring a 6–26 dB gain, overall yielding a 26.8–46.4 dB dB (V-mode)/89.6–109.2 dBΩ (C-mode) programmable gain range, with a 100 MHz bandwidth and a power and area consumption of 360.5 µW and 0.0177 mm2, respectively. This amplifier has been designed considering the constraints and specifications (including low voltage, low power, reduced noise and high common mode rejection ratio) for its use in an analogue Lock-in-based Frequency Response Analyser-Impedance Spectroscopy (FRA-IS) device. The proposed design introduces a novel fully differential open-loop structure based on a transconductance–transimpedance (TC-TI) topology for high performance applications with a broad programmable bandwidth. To compare this work, different figures of merit (FoMs) are introduced as well as a comparison table with other simulated and experimental results, reporting an overall better performance in terms of gain, frequency and power-area consumption.