SOI CMOS technology has been used to integrate analog circuits. In this chapter, operational amplifiers (op amps), filters, analog-to-digital converters (ADC) and digital-to-analog converters (DAC), sigma-delta ADC, RF circuits, low noise amplifiers (LNA), mixers, voltage-control oscillator (VCO), and high-temperature analog circuits using SOI CMOS technology are described.
In this section, SOI CMOS op amps are described. Starting from a single-stage op amp, a single-stage folded-cascode op amp is analyzed. Then, the performance comparison of op amps using bulk and SOI CMOS technologies is presented, and finally the advanced cascode op amp.
Figure 6.1 shows an SOI CMOS single-stage op amp with a symmetrical topology, which has a good capability to drive a large capacitive load , As shown in this figure, this SOI CMOS single-stage op amp is composed of an input differential pair (M 1, M2) and three current mirrors (M3-M8). Owing to a small threshold voltage, the current driving capability of SOI devices is large, which is suitable for high-speed operation of the op amp. In addition, the small parasitic capacitances at the source/drain may also help realization of the SOI CMOS op amps for high-speed operation.