Improved High-Input-Impedance mV-Amplifiers With Gain Factors From 10 to 900

New millivolt-amplifiers (mV-amplifiers) driving planar multijunction thermal converters (PMJTCs) at their output have been developed to measure the output voltage of micropotentiometers (mupots). Using a twin-stage design with gains of 10, 20, and 30 per stage, total gain factors ranging from 10 to 900 are achieved. This results in a usable range of input voltages from 100 muV up to 100 mV at frequencies ranging from dc to 1 MHz. A novel offset compensation results in small reversal differences, and this allows for reliable operation at higher gain factors. There is a sophisticated protection circuit to avoid damage of the PMJTC in the case of overload. The ac-dc transfer difference is flat within 100 muV/V up to 100 kHz.