On-chip Impedance Evaluation with Auto-calibration based on Auto-balancing Bridge

We propose a circuit mechanism with an auto-calibration in the impedance measurement circuit based on the auto-balancing bridge method. In the auto-balancing bridge method, an inverting amplifier circuit using an operational amplifier is used. Since the measurement accuracy depends on the feedback resistance of the inverting amplifier circuit, it is necessary to replace the feedback resistor each time as checking the measured value of the resistance of the DUT (device-undertest) so as to match the value. In this work, by employing a current-type D/A converter as a feedback resistor, we design a circuit with calibration of the resistance value and attain highly accurate measurement by simulation.