Novel current-feedback operational amplifier design based on a floating circuit technique

The conventional current-feedback op-amp (CFOA) exhibits high speed and high bandwidth but has relatively poor common-mode rejection ratio (CMRR) and poor DC offset and low frequency gain accuracy. Several design techniques improving the DC performance have been published. The proposed technique presented in this paper is to bootstrap the input stage with the input signal. By using this technique, the Early-effects in the input stage are almost eliminated, and as a result the DC performance including the CMRR is substantially improved. By virtue of the improved DC and CMRR performance, the gain accuracy is increased by about ten times. All of the improvements are obtained without apparent increase in the circuit size and power consumption, and consequently without degrading the noise performance.