Calibration circuit for accurate determination of the output impedance of an integrated circuit has a voltage divider with a reference resistance and adjustable resistance which is calibrated against the reference voltage

摘要

Calibration circuit (1) for accurate setting of the output impedance of an integrated circuit has a voltage divider with an adjustable resistance (R) in series with a reference resistance (Rref). A voltage tap from between the two is connected to the input of a comparator (3). The other input (Vcomp) to the comparator is taken from the output of a comparison circuit (2). The output of the comparator is input to controller (6) which adjusts the adjustable resistance until the voltage fed to the comparator from the voltage tap is equal to the comparison voltage.