Design of bulk driven miller Operational Transconductance Amplifier

This paper presents a simple technique to enhance the gain of Operational Transconductance Amplifier (OTA) operating at a low voltage. In conventional OTA, bulk driven differential pair is used for low voltage operation. However, it introduces a reduction in the g_mb/g_m ratio. The gain of OTA can be enhanced by increasing its transconductance. The proposed work uses input bulk-driven differential pair operating in weak inversion with positive feedback source degeneration technique to achieve a higher transconductance. This improves the gain of OTA without any change in the power consumption. A DC gain of 63 dB and a power consumption of 86.70 pW is obtained with a unity gain frequency of 4.87 Hz using 250nm CMOS technology at 2.5 V.