Design and Analysis of a Two stage Class AB Operational Trans-conductance Amplifier in 180 –nm Technology

This paper presents design concept of Operational Transconductance Amplifier (OTA). Using active loads in the first stage and improved recycling structure, the effective trans-conductance of the first stage is increased. Nonlinear current mirror boosts the current of the second stage; Therefore, Slew Rate (SR) is increased. The class-AB technique is achieved without enhancing power dissipation and without unity-gain bandwidth (UGBW) or noise deterioration. The efficiency of the proposed OTA is evaluated by several simulations in a 0.18μm CMOS process with the 1.8 V supply voltage. This technique is very helpful for high amplification, stability, and low power applications. From the simulation results, the two stage amplifier gives better performance compared to other topologies, especially in terms of gain, output swing, slew rate and unity-gain bandwidth. The circuit is able to achieve 95 dB gain, a 3V output swing, a 169 slew rate and a unity-gain bandwidth of 344 MHZ with a power supply voltage of 1.8 V.