Compact CMOS Wideband Instrumentation Amplifiers for Multi-Frequency Bioimpedance Measurement: A Design Procedure

Abstract

The design of an instrumentation amplifier (IA), based on indirect current feedback and suited to electrical bioimpedance spectroscopy, is presented. The IA consists of two transconductors and a summing stage, featuring a single-stage configuration process that allows the maximum achievable bandwidth to be extended. The transconductors are linearized by means of resistive source degeneration, whereas the use of super source followers allows a reduction in the values of the source degeneration resistors. This fact leads to a decrease in the overall noise and the silicon area, thus resulting in a compact implementation. A thorough analysis of the proposed solution, accompanied by a design procedure and verified by means of electrical simulations, is also provided. Two versions of the IA, i.e., a single-ended (SE) and a pseudo-differential (PD) structure, were designed and fabricated using 180 nm CMOS technology to operate with a 1.8 V supply. The experimental results, including a BW of 5.2 MHz/8.0 MHz, a CMRR higher than 72 dB/80 dB, a DC current consumption of 139.0 μA/219.3 μA and a silicon area equal to 0.0173 mm2/0.0291 mm2 for the SE/PD implementation, validate the suitability of the approach.

1 V Electronically Tunable Differential Difference Current Conveyors Using Multiple-Input Operational Transconductance Amplifiers

“…Voltage-to-current (V-to-I) converters, the so-called transconductors, are useful basic building blocks for realizing analog filters, oscillators, gyrators, and instrumentation amplifiers; for examples see [52][53][54][55][56]. In this work, the proposed EDDCC has been used to realize the V-to-I converter as shown in Figure 5.…”

Amplifiers in Biomedical Engineering: A Review from Application Perspectives

“…In another study, an indirect current feedback method was presented for conducting bioimpedance measurements [ 69 ]. It uses degeneration resistors where the resistors are low.…”

Wide-Bandwidth Electronically Programmable CMOS Instrumentation Amplifier for Bioimpedance Spectroscopy

“…Thus, matching must be enhanced in order to improve the CMRR. An outstanding feature of a current feedback IA is that the CMRR relies fundamentally on the input transconductor [31]. Indeed, all the devices in the input V-to-I converter, G mI , take part in the generation of the residual transconductance in (9).…”

“…The biological impedance (Z BIO ) is excited by an electrical sinusoidal signal, either a current or a voltage, the corresponding magnitude (a voltage or a current, respectively) is measured, and the internal composition of the Z BIO is derived from the gain and phase angle of the response. In many applications, an excitation current, i exc , is preferred, in order to avoid damaging the biological media, and a voltage is measured in response with the assistance of an instrumentation amplifier (IA) [2]- [31], as illustrated in Fig. 1.…”

“…The indirect current feedback (ICF) technique, represented by the block diagram within the dotted box in Fig. 1, is a suitable approach to implement a monolithic IA able to operate in a low-voltage supply environment [6], [27], [29], [31]. A single-stage ICF IA is basically made up of an input and an output (or feedback) transconductor, G mI and G mO in Fig.…”