Low-voltage, low-power and high gain CMOS operational transconductance amplifier

A low voltage, high DC gain and wideband load compensated cascode operational transconductance amplifier (OTA), using an active positive feedback with feedforward technique and frequency-dependent current mirrors (FDCM), is presented and analyzed. Such techniques stand as a powerful method of gain, bandwidth and phase margin enhancements. In this paper, a frequency-dependent current mirror, whose input impedance increases with frequency, is used to form the feedforward path at the input of the current mirror with a feedforward capacitor. By using these techniques, the gain bandwidth product of the amplifier is improved from 115 MHz to 194 MHz, the phase margin is also improved from 85° to 95° and the gain is enhanced from 11 dB to 93 dB. This amplifier operates at 2.5 V power supply voltage, drives a capacitive load of 1 pF and gives a power dissipation of 7 mW. The predicted performance is verified by simulations using HSPICE tool with 0.8 μm CMOS AMS parameters.