In this paper, inverse mode operation of class-J amplifier is introduced. Performances such as dc power dissipation, ac output power, and drain efficiency of the inverse mode class-J are compared with the ones of regular class-J operation. Because of the reduced overshoot in the drain current, the minimum drain voltage in inverse class-J mode can be lowered, so that the output power and drain efficiency are improved. The analysis shows that better efficiency is achieved as the minimum drain voltage is lowered below the knee voltage. For the verification, class-J and inverse class-J power amplifiers at 900MHz are implemented. The experimental results show that the efficiency of the inverse class-J amplifier is 66.2% whereas the conventional class-J operation shows 61.2%. This work is expected to be useful for the design of efficient power amplifiers with reasonable linearity.