A novel frequency compensation technique for three-stage amplifiers is introduced. The proposed solution exploits two Miller capacitors, two resistors and an additional feedforward stage which can be implemented without entailing extra transistors. Design equations using the phase margin as design parameter are carried out. The technique is used to design, with a standard CMOS 0.35-μm process, a 2-V three-stage amplifier driving a 500-pF load capacitor. The amplifier dissipates only 70 μA at DC and achieves a 1.2-MHz gain-bandwidth product, showing a significant improvement in (MHz·pF)/mA performance.
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