Negative Resistance Active resistor with Improved linearity and Frequency Response

An original active resistor circuit will be presented. The main advantages of the new proposed implementations are the improved linearity, small area consumption and improved frequency response. An original technique for linearizing the I(V) characteristic of the active resistor will be proposed, based on the utilization of a new linear differential amplifier, and on a current-pass circuit. The linearization of the original differential structure is achieved by compensating the quadratic characteristic of the MOS transistor operating in the saturation region by an original square-root circuit. The errors introduced by the second-order effects will be strongly reduced, while the circuit frequency response of the circuit is very good as a result of operating all MOS transistors in the saturation region. In order to design a circuit having a negative equivalent resistance, an original method specific to the proposed implementation of the active resistor circuit will be presented. The circuit is implemented in 0.35 μm CMOS technology, the SPICE simulation confirming the theoretical estimated results and showing a linearity error under a percent for an extended input range (± 500 mV) and a small value of the supply voltage (± 3 V).