New Input Offset Voltage Measurement Setup for Ultra Low-Voltage Fully Differential Amplifier

This paper deals with the measurement of input offset voltage of a fully differential low-voltage variable gain amplifier intended for on-chip systems. A new measurement setup that effectively separates the output common and differential mode signals was developed. By only using the differential output voltage in the feedback path, any common mode errors are effectively suppressed. As the gain of the device to be measured was expected to be relatively low, an auxiliary loop amplifier was introduced in each feedback path to increase the loop gain of the circuit as well as reduce loading of the device under test. This effectively reduces measurement errors caused by the non-ideal parameters of the device under test. A test board was developed and verified by the measurement of bare-die samples. Slight deviation of results when compared to simulated data was observed. This is likely due to the use of probe needles, which results in varying contact quality and a rather small number of samples available for measurement.