Externally linear current amplifiers

This paper describes a method to implement externally linear internally non-linear (ELIN) current amplifiers. Two novel schemes of ELIN current amplifier circuits are proposed, including hyperbolic sine (SINH) and hyperbolic tangent (TANH) circuits. The obtained linear input-current ranges of SINH and TANH circuits are 400 Ap-p with total harmonic distortion (THD) less than 2% and 140 Ap-p with THD less than 0.2%, respectively, both at the input frequency 1 kHz. Also, the current gains of the proposed circuits can be varied either in positive or negative region by adjusting the dc bias currents. Their current gains are tunable in the range of -10 A/A to 10 A/A and insensitive to temperature. Simulation results show that the performance of the circuits are as good as expected.