A compensation strategy for two-stage CMOS opamps based on current buffer

The compensation with current buffer overcomes the typical drawbacks of the compensations based on nulling resistor or voltage buffer, but it is not as straightforward as the other two approaches. Indeed, a constraint on the current-buffer input resistance has to be met in order to achieve frequency compensation, since complex conjugate poles arise in the loop transfer function. Design equations for an optimized compensation strategy with current buffer are determined. They allow a high gain-bandwidth product to be achieved avoiding the drawbacks which arises with voltage buffer and nulling resistor approaches.

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