This paper describes a 863-870-MHz transmitter for wireless sensor applications. The fully integrated designed circuit is based on AMS0.35-mu mCMOS standard technology. The transmitter presented is composed by four stages: quadrature voltage-controlled ring oscillator (QVCO) controlled by a voltage (V-CTRL), two passive switch mixers, two combiners (a substractor and an adder), and a novel high linear power amplifier (PA). Combiners and the PA has the distinction of being based on CMOS inverter circuit. The post-layout simulation of the fully differential transmitter, at the desired oscillation frequency and under a supply voltage of 3.3 V, shows that proposed circuits satisfy specifications desired especially the output power level and PA linearity.