An adjustable CMOS floating resistor

A floating node resistor has a wide range of usage in analog integrated circuits. In this paper, we propose a new CMOS linear floating resistor circuit which is based on a transconductor circuit. The proposed circuit topology is capable of implementing both positive and negative resistance. The introduced floating resistor has simple circuit implementation and its resistance is tunable by adjusting the gate voltage of a MOS transistor. PSpice simulation results show that the example circuit made by AMI 1.5 μm CMOS process presents a constant resistance of 2.6 MΩ to 5.1 MΩ when the adjust voltage ranges from −3.4 V to −2.4 V and the corresponding adjusted current is 16 μA to 57 μA, with ±5V voltage supplies. The cutoff frequency is about 1 MHz.