A New Fast Rail-to-Rail Continuous-time Common-Mode Feedback Circuit

S. Mahdavi, F. Noruzpur (Urmia Graduate Inst., Iran), E. Ghadimi (Islamic Azad Univ., Iran), T. Moradi Khanshan (Urmia Univ., Iran)

A novel and reliable rail-to-rail continuous-time Common-Mode Feedback Block (CMFB) circuit for low voltage, large output swing, and high-speed applications is presented in this paper. The main aims of the proposed idea are achieving high accuracy, high linearity and high-speed CMFB accompanied wideband dynamic range and large output swing as well. Hence, as MATLAB simulation results prove, employing the reference voltage (Vref) from 0.50 to 1.40 volts on the suggested CMFB, it can adjust the output voltage of the amplifier to the appropriate level with low error properly. Furthermore, applying the worst case simulation (initial condition 0 and 1.8 volts) on the proposed CMFB circuit, the output voltage can be settled in the desired level just after 1.33ns noticeably. The settling time error and the power consumption of the suggested common-mode feedback circuit are just 88µVand 216µW with the power supply of 1.8 volts respectively. Also, DC gain and phase margin of the amplifier are 61dB and 70.5 degree correspondingly, and 0.5pF capacitor load is applied to the output nodes of the amplifier. Meanwhile, the proposed idea is a good candidate for low voltage and large output swing applications too. Because it just needs lower than 3 overdrive voltage (ΔV) to start its performance. Finally, the proposed circuit is simulated in whole process corner condition and different temperatures in the region from -55℃ to +65℃. Simulation results are performed using the HSPICE BSIM3 model of a 0.18µm CMOS technology and MATLAB software.