Design Of CMOS References And Amplifiers Based On High-Speed CMOS D/A Converter

In the areas of the mixed-signal IC and analog IC, as an important block in data converters, reference circuits will always be the research hotspot in future. This thesis designs three current reference sources which are applied in 1.8v current-steering digital-to-analog converter. The design of these current sources include two parts, one is the voltage reference source which generate a stable output voltage and the other is the V-I converter circuit which convert the reference voltage to reference current.Firstly, principles of reference IC and how to obtain better temperature stability are analyzed in this paper. Then, typical band-gap reference voltage used in DAC is designed and analyzed. Based on the disadvantages of typical band-gap reference voltage, a band-gap reference used in low voltage and a non-band-gap reference are designed. As the first-order temperature compensation circuit features are not ideal, power supply rejection ratio of non-band-gap reference voltage circuit is very low, this article increases circuits to improve power supply rejection ratio and temperature coefficients, so that the reference voltage sources have a good temperature features and characteristics of power supply rejection ratio. Temperature coefficients of these two reference circuits are 1.77ppm/℃and 15.5ppm/℃, and the Power supply rejection ratio are -137.35dB and -76.34dB respectively.Based on the above-designed voltage reference circuits, this thesis designs three CMOS current reference circuits with good stability and high precision used in DAC.Two compensation methods are introduced, through the combination of a PTAT current and a negative temperature coefficient current and through the compensation of two types of resistances to get more stabilized currents. Based on the SMIC 0.18um Process, The temperature characteristics of three current references are simulated, simulation results show that the first circuit can provide an output current reference with a variation 800nA over a temperature range from -25 to 75°C, the second circuit changes around 790nA from -20-95oC, and the last one can provide an output current reference with a variation 400nA over a temperature range from -25 to 90°C, these equate to a 0.33%,0.32% and 0.16 % change in output current respectively. The simulation results show that the reference circuit can supply current biased voltage for the 1.8v current-steering digital-to-analog converter.