The invention relates to an electrical circuit for an access control of an immobilizer system of a vehicle and a method for calibrating an antenna driver. There is provided an electric circuit for an access control for an immobilizer of a vehicle. The electrical circuit includes a first antenna driver (12) for driving a first antenna (19) for transmitting a signal (100) in the case of identifying an ID transmitter (3) for access control of a vehicle. A second antenna driver (24) is provided for driving a second antenna (21) for transmitting a signal (104) in the case of identifying an ID transmitter (3) for the immobilizer of the vehicle. In addition, the electrical circuit includes a receiver means (14) for receiving one of an antenna (21) the received signal to identify an ID transmitter (3) for the immobilizer. The first antenna driver (12) and the receiver means (14) are together in one semiconductor chip (1) is integrated.