a method of calibrating a polar amplification stage including a main signal path and a magnitude signal path , the method comprising : generating signals for the main signal path and the magnitude signal path for operating an amplifier between a linear mode of operation and a saturated mode of operation ; detecting first and second peaks in a signal at the output of the amplifier representing transitions between the linear and saturated modes of operation ; and adjusting the timing in one of the main signal path and the amplitude signal path in dependence on a relative difference between the size of the detected first and second peaks .