AN SFQ DIGITAL-TO-ANALOG CONVERTER

We have developed and demonstrated a digital to analog converter DAC w hich uses an SFQ counter to precisely divide an input reference oscill ator to produce a set of binary frequencies/voltages. The binary input gates the output SFQ pulses of the counter flip flops to a passive su mming network, producing an analog output current. The DAC is asynchro nous (no clock to reset latching circuits), low power, and requires on ly N equal matched resistors. We have built and tested a 4-bit Nb DAC with data clocking rates up to 1 GHz. Using the DAC we have generated arbitrary wave forms including ramps and sine waves. By measuring the harmonic content of sine wave outputs, we deduce values for the DAC li nearity.