On-electrode autonomous current generator for multi-frequency EIT

Abstract

The paper presents an autonomous programmable current generator module for multi-frequency EIT systems. The module incorporates all stages from the sine wave generation with frequency and amplitude tuning, D/A converter and filter, a high output resistance voltage-to-current converter to the associated digital communication and control. The paper presents in depth the original digital quadrature signal generator and the output current generator with a high resistance. The other main blocks of the design use current practice specifications, since recent technological solutions proposed in the literature were found appropriate. The proposed signal generator circuit, characterized by a very low complexity, is analyzed in its capacity to produce multiple accurate signals up to 1 MHz in frequency. The precision output current source uses a modified current conveyor of type CCII with a high output resistance and low distortion. The output current frequency spectrum and linearity parameters obtained in the simulations are also described. The simulation results indicate a good linearity and high output resistance with an acceptable output voltage swing. The calculated performance parameters are validated with simulations, and future work for the prototype fabrication of the IC is outlined.

Current-conveyor-based wide-band current driver for electrical impedance tomography

“…The current I X is mirrored to the output of the current-controlled current source, and I Z = I X flows through a DC-blocking capacitor, C block , to an electrode and into the tissue. Our current driver architecture (figure 3) is based on the work presented in Jivet and Dragoi (2008). We modified the original architecture to make it suitable for high frequency EIT applications.…”

“…(c) Current is mirrored to the high output impedance terminal Z with a gain enhanced current mirror forming the output stage. Figure 2 shows the architecture of the implemented current source which is based on [12]. The voltage to current conversion is performed using a 2-stage opamp in unity gain configuration.…”

The differential Howland current source with high signal to noise ratio for bioimpedance measurement system

“…14 In the single-ended output current source circuit, the noise level mainly depends on the input signal and the anti-noise performance of the operational amplifier. [16][17][18] In this paper, we propose a novel differential current source circuit based on the Howland topology current source circuit. First, the performance of the Howland and differential current circuits were analyzed.…”

Low power current sources for bioimpedance measurements: a comparison between Howland and OTA-based CMOS circuits

“…High performance current sources with wide bandwidths based on operational amplifiers have been widely developed and can be found throughout the literature (29)(30)(31) while others have used integration techniques for developing current sources (32)(33)(34)(35)(36)(37). An integrated realization of a Voltage-Controlled Current Source (VCCS) for bioimpedance applications (33,38,39), which are based on the operational transconductance amplifier (OTA) approach. Our targeted measuring applications require an operating frequency band of 1 kHz to 1 MHz and current amplitudes of up to 500 μA p (peak).…”