A low-voltage operational amplifier with high slew-rate for sigma-delta modulators

This paper presents the design of a low-voltage operational amplifier suitable for sigma-delta (/spl Sigma//spl Delta/) modulator applications. The circuit technique is proposed to enhance the slew-rate performance and correspondingly can help to save the power of the amplifier. The simple circuitry of a current mirror is included with a degenerate resistor that can be selectively shunted. High-speed 2nd-order /spl Sigma//spl Delta/ modulators incorporating this technique is designed in a 0.18-/spl mu/m CMOS technology and power consumption can be saved more than 20% for a power supply voltage of 1.2V.Joongho Choi; Jinup Lim; Cheng Chew Li