Low-voltage CMOS Current Feedback Amplifier

The paper presents the design of a novel low-voltage CMOS Current-Feedback Operational Amplifier (CFA). The circuit has been designed using a standard 0.35 mu m CMOS process and is capable of operating at a supply voltage of 1.8 V with an input common mode range of 0.3 to 1.6 V. The proposed circuit is based on a modified CCII+ model and incorporates a constant-gm complementary input stage in order to achieve high linearity across a wide range of input voltages. Furthermore, this feature enables the CFA input stage to maintain an almost constant inverting input impedance of 32 Omega and an open loop voltage gain of 75 dB. Circuit simulations indicate that the proposed CFA can achieve a gain-bandwidth (GBW) of 470 MHz and a slew rate of 387 V/mu s, with a phase margin of at least 70 degrees when simulated at a nominal closed loop gain of 10 and under open circuit output condition. The corresponding GBW and slew rate values for 2 pF capacitive load are 418 MHz and 386 V/mu s respectively.