This paper investigates memory effects in RF transmitters due to the high-power amplifiers (HPA). Phenomena such as asymmetries in lower and upper intermodulation terms, and variation of nonlinear characteristic, depending on signal history, are usually observed at the output of high-power amplifiers. These effects have been practically investigated using a 3.5-GHz N-channel enhancement-mode lateral MOSFET power amplifier and different signals such as two-tone and multicarrier OFDM.