Abstract
Current drivers are fundamental circuits in bioimpedance measurements including electrical impedance tomography (EIT). In the case of EIT, the current driver is required to have a large output impedance to guarantee high current accuracy over a wide range of load impedance values. This paper presents an integrated current driver which meets these requirements and is capable of delivering large sinusoidal currents to the load. The current driver employs a differential architecture and negative feedback, the latter allowing the output current to be accurately set by the ratio of the input voltage to a resistor value. The circuit was fabricated in a 0.6- μm high-voltage CMOS process technology and its core occupies a silicon area of 0.64 mm (2) . It operates from a ± 9 V power supply and can deliver output currents up to 5 mA p-p. The accuracy of the maximum output current is within 0.41% up to 500 kHz, reducing to 0.47% at 1 MHz with a total harmonic distortion of 0.69%. The output impedance is 665 k Ω at 100 kHz and 372 k Ω at 500 kHz.
Highlights
E LECTRICAL IMPEDANCE TOMOGRAPHY (EIT) offers particular promise in the assessment of neonatal lung function because it is as a non-invasive imaging method requiring no collaboration from the infant [1]–[4]
A high power integrated current driver implemented in a 0.6- m standard HV CMOS technology has been presented
The circuit features a pair of balanced current drivers in a negative feedback configuration for monitoring and regulating the output current
Summary
E LECTRICAL IMPEDANCE TOMOGRAPHY (EIT) offers particular promise in the assessment of neonatal lung function because it is as a non-invasive imaging method requiring no collaboration from the infant [1]–[4]. Its maximum output current was limited to 350 A p-p with an accuracy of 1% at 90 kHz. The integrated current driver presented in [21] used an open loop operational transconductance amplifier (OTA) with an active inductive load. The integrated current driver presented in [21] used an open loop operational transconductance amplifier (OTA) with an active inductive load It achieved an output impedance in excess of 500 k at 500 kHz but its maximum output current was limited to 500 A p-p. This paper is an expansion of [25] and presents the complete design and test results of the fabricated current driver chip implemented in a 0.6- m high-voltage (HV) CMOS process technology.
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