A new frequency compensation method based on differential current conveyor

Abstract

A new frequency compensation scheme using a second generation differential current conveyor (DCCII) for three-stage amplifiers is proposed. By adding a DCCII as a feedback path from output of the second and the third stage to the output of the first stage, feed-forward path and the right-half plane zero will be removed subsequently which improves phase margin and the gain-bandwidth product. Calculations are derived for two states. First state, a DCCII and two miller capacitors form the feedback paths and in the second state, two nulling resistors are series with miller capacitors. Analyses show that in both states, stability can be perfectly ensured. To demonstrate advantages of this technique over the traditional RNMC architecture, a three-stage amplifier is designed and simulated employing the proposed technique in a standard 0.18μm CMOS process. Simulation results show that, with the same load capacitance, the new amplifier has improved stabilities over the conventional RNMC amplifiers by more than 22° and 0.23MHz in the phase margin and gain-bandwidth product, respectively. The proposed amplifier dissipates less than 0.45 mW of power with a 1.8 V supply.