2008/12/01 by Johan F. Witte, J.F. Witte, Johan H. Huijsing +1
Engineering · #Analog and Mixed-Signal Circuit Design #Magnetic Field Sensors Techniques #Advancements in Semiconductor Devices and Circuit Design
paper · doi:10.1109/jssc.2008.2005695
This paper describes an instrumentation amplifier for bidirectional high-side current-sensing applications. It uses a multipath indirect current-feedback topology. To achieve low offset, the amplifier employs a combination of chopping and auto-zeroing in a low frequency path to cancel the offset of a wide-band amplifier in a high frequency path. With a 60 kHz chopper clock and a 30 kHz auto-zero clock, this offset-stabilization scheme results in an offset voltage of less than 5 muV , a CMRR of 143 dB and a common-mode input voltage range from 1.9 to 30 V. The input voltage-to-current ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V-I</i> ) converters required by the current-feedback topology are implemented with composite transistors, whose transconductance is determined by laser-trimmed resistors. This results in a less than 0.1% gain inaccuracy. The instrumentation amplifier was realized in a 0.8 mum BiCMOS process with high voltage transistors, and has an effective chip area of 2.5 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .