Tunable linear CMOS current mirror

Abstract

Based on triode MOSFETs as tunable devices, a tunable linear current mirror is proposed, whose current gain is tunable over a wide range. Simulations show that, total harmonic distortion on the output current is within 2% for a tuning range of almost five octaves. Although the structure is in the form of an active-input current mirror, keeping the tuned MOSFETs in triode region significantly relaxes the stability problems of an active-input current mirror. This issue is revealed by theoretical analyses and further simulations are included for demonstration. An application example is also supplied.

Electronically Adjustable Current Mirrors

“…For this purpose, a number of adjustable current mirror topologies have been already introduced in the literature [1][2][3][4][5][6]. However, all these realizations have at least one of the following drawbacks:…”

“…• Absence of low-voltage operation capability [3] • Limited range of gain adjustment [5] • Employment of PMOS transistors for handling ac signals [ [1,3,4,6] • Limited bandwidth and/or several restrictions imposed by the utilization of MOS transistors operating in weak inversion or triode region [4,6] • Requirement of a specific nonlinear form of input currents [2] In contrast with previous implementations, the proposed scheme of current mirror simultaneously offers low-voltage operation capability employment of only NMOS transistors biased in strong inversion, absence of any imposed restrictions concerning the input current and bidirectional adjustment of gain.…”