A 10 bit cryogenic CMOS D/A converter

A 10 bit cryogenic current steering D/A converter (DAC), operating from room temperature to as low as 4.2K temperature, is presented here. The converter is primarily designed for a Silicon (Si) quantum computer controller circuit for initializing quantum bits (qubits). A new analog calibration method with an on chip reference current generator is applied to all the bits of the converter to overcome the nonlinearity and mismatch errors of the current sources in low temperature. The converter drives a 50 ohm load to 0.5V while its average power consumption is about 32mW from a 3V power supply. The cryogenic DAC's differential nonlinearity (DNL) is plus minus 0.27 LSB and integral nonlinearity (INL) remains within -0.49 and 0.41 LSB. The complete system is designed, simulated and laid out using a commercial standard 0.5 micro meter Silicon-on-Sapphire (SOS) CMOS process.