Improving capacitive drive capability of two-stage op amps with current buffer

A frequency compensation technique for two-stage amplifiers with a current buffer is introduced, which separates the large load capacitance at the output from the feedback node with a resistor. The proposed compensation technique is analyzed and compared to a traditional separation resistor approach using small signal analysis and simulations in 0.35μm CMOS process. It is shown that with moderate and heavy capacitive loads the proposed technique has considerable bandwidth and stability advantages over the traditional technique. These improvements arc achieved at the expense of adding an additional package pin, if the separation resistor is located off chip.