Improving power efficiency of a two-stage operational amplifier for biomedical applications

By using compensation technique with feed-forward path, an improved folded cascode operational transconductance amplifier (OTA) that operates in weak inversion region is designed. The proposed configuration consists of composite transistors, recycling structure and feed-forward compensation path. In comparison with the typical folded cascode CMOS Miller amplifier, this design has higher DC gain, unity gain frequency and slew rate without adversely affecting the noise and offset performance. The presented OTA is simulated in 0.18 mu m CMOS technology and the simulation results confirm the theoretical analyses. Finally, the proposed amplifier has a 104.5 dB open-loop DC gain and 69.4 kHz unity gain frequency @ 0.6 V supply voltage while the power consumption is 300 nW.