An apparatus for determining information on an amplitude error of a transmit signal includes at least one transmit path module, at least one feedback receive path module and at least one error determining module. The transmit path module generates a high frequency transmit signal based on a baseband transmit signal. The feedback receive path module generates a baseband feedback signal based on a high frequency feedback signal derived from the high frequency transmit signal. Further, the error determining module determines an error signal indicating information associated with an amplitude error of the high frequency transmit signal based on the baseband transmit signal and the baseband feedback signal. The error determining module comprises a feedback loop. This feedback loop of the error determining module comprises a feedback loop processing module. The feedback loop processing module generates a feedback loop output signal based on a feedback loop input signal and the baseband transmit signal.