Low-Voltage SOI CMOS VLSI Devices and Circuits

6

SOI CMOS Analog Circuits

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.

6.1 SOI OP AMPS

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.

6.1.1 Single-Stage 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 [1], 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.

Fig. 6.1 SOI CMOS single-stage op amp with a symmetrical topology, which has a good capability to drive ...