A power amplifier circuit can be linked to an antenna arrangement of a communication system for transmission of ASK RF data signals. The power amplifier circuit includes an amplifier core with several cascode amplifier cells in parallel. Each cascode amplifier cell is composed of three NMOS transistors in triode mounting between an output terminal connected to the antenna arrangement, and an earth terminal. A first transistor of each cascode amplifier cell is controlled by a carrier frequency signal, whereas a second transistor of each cascode amplifier cell is controlled by a smoothing control loop in order to modulate data to be transmitted on carrier frequency by amplitude shift keying. The smoothing control loop is provided for generating an increasing gate voltage for the second transistors on the basis of an increasing current ramp from a first minimum current value to a second maximum current value during a "0" to "1" data transition. The smoothing control loop is provided for generating a decreasing gate voltage for the second transistors on the basis of a decreasing current ramp from the second maximum current value to the first minimum current value during a "1" to "0" data transition for shaping the envelope of ASK RF data signals to be transmitted.