This paper presents a fully integrated low power class-E power amplifier and its integration to remotely powered sensor system. The on-chip 1.2 GHz power amplifier is implemented in 0.18 A mu m CMOS process with 0.2 V supply. The implantable system is powered by using an inductively coupled remote powering link at 13.56 MHz. A passive full-wave rectifier converts the induced AC voltage on the implant coil into a DC voltage. A clean and stable 1.8 V supply voltage for the sensor and communication blocks is generated by a voltage regulator. On-off keying modulated low-power transmitter at 1.2 GHz is used for the transmission of the data collected from the sensors. The transmitter is composed of a LC tank oscillator and a fully on-chip class-E power amplifier. Compared to the conventional class-E power amplifiers, an additional network which reduces the on-chip area is used at the output of the power amplifier. The measurement results verify the functionality of the remotely powered implantable sensor system and the power amplifier. The integrated power amplifier provides -10 dBm output power for 50 Omega load with a drain efficiency of 31.5 %. The uplink data communication with a data rate of 600 kbps is established by using a commercial 50 Omega chip antenna at 1 m communication distance.