A cryogenic D/A converter with novel charge injection reduction technique for silicon quantum computer controller circuit

Silicon quantum bits (qubits), operated in deep cryogenic temperature (typically ≤ 500mK), need rapid pulse generation circuits for quantum gate operations. We have designed a ±1.5V 10 bit cryogenic CMOS high speed current steering D/A converter which outputs both positive and negative analogue signals to trigger these qubits. Instead of using a current mirror at the output stage, a source and a full complementary sink structure are used to ensure lower power dissipation and to get fast output levels. Then to compensate the mismatch effects of current sources and to confirm that there are no missing analogue output steps (like missing code in an A/D converter), we have utilized an analogue charge storage based calibration method and extended the full calibration procedure to the least significant bits (LSB´s). A novel charge injection reduction technique is presented in this paper that allows the analogue memory (stored charge on the gate capacitance of a MOSFET) to balance the nonlinearity problem caused by charge injection. The whole system has been designed and simulated using a standard 0.5μm CMOS Silicon-on-Sapphire (SOS) process.