Hello,
Power semiconductor components in PLECS are based on ideal switches, so unfortunately our tool is not designed to model amplifier circuits where the device is operating in the linear range (it is either off or no). You would need to develop logic that represents the amplifier switch in this case, such as by using a lookup table, rather than including the PLECS MOSFET. Further, the gate signal input port of the MOSFET requires a (green) Control domain signal, not an electrical (black) connection.
Regards,
Kris