A low-offset high CMRR current-mode instrumentation amplifier using differential difference current conveyor

Current-mode circuits are generally desirable for their high bandwidth. Moreover, current-mode instrumentation amplifiers have an advantage over voltage-mode counterparts that, they do not require precise resistor matching for a high CMRR. In this work, a current-mode instrumentation amplifier is proposed by employing Differential Difference Current Conveyor (DDCC). The proposed structure employs a single DDCC element, and an operational amplifier is used as a buffer or a final amplifier stage. After the explanation of the circuit, redundant output feedback (ROFB) circuit is presented to increase CMRR and to overcome the offset voltage at the output of the DDCC. The DDCC element is designed with 0.35μm technology and the proposed circuits are simulated using HSPICE. The proposed circuit with the feedback path provides more than 110 dB CMRR value at 1 MHz which is much higher than other current-mode implementations.