An ultra-low-power CMOS symmetrical OTA for low-frequency Gm-C applications

In this paper an ultra-low-power CMOS symmetrical operational transconductance amplifier (OTA) for low-frequency Gm-C applications in weak inversion is presented. Its common mode input range and its linear input range can be made large using DC shifting and bulk-driven differential pair configuration (without using complex approaches). The symmetrical OTA was successfully verified in a standard CMOS 0.35-μm process. The measurements show an open loop gain of 61 dB and a unit gain frequency of 195 Hz with only 800 mV of power supply voltage and just 40 nW of power consumption. The transconductance is 66 nS, which is suitable for low-frequency Gm-C applications.