A novel linear resistor utilizing MOS transistors with identical sizes and one controlling voltage

A new voltage-controlled active resistor is presented in which the simple circuit of an MOS transistor operating in the ohmic region and connected in parallel with another MOS transistor operating in the saturation region is linearized by a novel ‘linearization improvement circuit’ (L1C). The proposed circuit utilizes only a single external voltage to control the active resistor through its full range. Furthermore, the proposed circuit employs five MOS transistors with identical sizes and shape factors, which makes manufacturing feasible. Simulation results using SPICE 3E.2 are shown. As an application example using this proposed device, a fourth-order high pass filter with tuneable cut-off frequency is presented and its characteristic compared with that of a circuit containing passive resistors