High Gain Amplifier with Enhanced Cascoded Compensation

A two-stage CMOS operational amplifier with both, gain-boosting and indirect current feedback frequency compensation performed by means of regulated cascode amplifiers, is presented. By using quasi-floating-gate transistors (QFGT) the supply requirements, the number of capacitors and the size of the compensation capacitors respect to other Miller schemes are reduced. A prototype was fabricated using a 0.5 mu m technology, resulting, for a load of 45 pF and supply voltage of +/- 1.65 V, in open-loop-gain of 129 dB, 23 MHz of gain-bandwidth product, 600 phase margin, 675 mu W power consumption and 1% settling time of 28 ns.