A DIFFERENTIAL-INPUT, DIFFERENTIAL-OUTPUT CURRENT MODE OPERATIONAL-AMPLIFIER

A current operational amplifier with differential input and differential output is described. The amplifier is based on the parallel connection of a CCII+ current conveyor and a CCII- current conveyor followed by a differential output transconductance gain stage. The performance of the amplifier is analysed and experimental results obtained from an implementation using standard operational amplifiers and current mirrors realized using transistor arrays are presented and compared to the theoretical analysis. It is concluded that the static small signal open loop gain and the frequency response matches the performance of conventional voltage operational amplifiers. The input offset and bias errors and the common mode rejection are shown to be strongly dependent on the matching accuracy of the current mirrors used in the conveyors. The proposed configuration can easily be integrated into a monolithic amplifier in either CMOS or bipolar technology.