High performance current mirrors using quasi-floating bulk

In this paper, a modified structure of standard MOSFET is proposed which offer high transconductance in comparison to its conventional architecture. The conventional MOSFET is a four terminal device whose fourth terminal, the bulk is connected to either negative/positive supply for N-channel/P-channel transistor respectively, or to their source terminal. In the proposed structure, instead of connecting bulk to supply rails or to source terminals, the bulk is configured in a quasi-floating state and then connected back to its gate terminal. The resultant is a gate driven quasi floating bulk MOSFET. Under DC analysis, the proposed structure operates as standard gate driven MOSFET whereas performing analysis in frequency domain the structure results in effective transconductance higher than that of standard MOSFET. Using the proposed structure, three high performance current mirrors are presented in this paper which showed improved performance over its conventional architectures. Performance of the proposed structure and the current mirror circuits are verified using HSpice simulations on 0.18 µm mixed-mode twin-well technology at a supply voltage of ±0.5 V.