Low-voltage CMOS current feedback amplifier

Abstract

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 μm 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 Ω 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/μs, with a phase margin of at least 70° 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/μs respectively.