We propose a new high speed and low power SOI inverter with dynamic threshold voltage that can operate with efficient body-bias control and free supply voltage. The performance of the proposed circuit is evaluated by both the BSIM3SOI circuit simulator and the ATLAS device simulator and then compared with other reported SOI circuits. The proposed circuit is shown to have excellent characteristics. At the supply voltage of 1.5 V, the proposed circuit operates 27% faster than the conventional SOI circuit with almost the same power dissipation. (C) 1999 Elsevier Science Ltd. All rights reserved.