A circuit for amplitude modulating a carrier signal includes a carrier signal input, circuitry for splitting the carrier signal into first and second paths, circuitry for phase modulating the carrier signal on the first path, circuitry for phase modulating the carrier signal on the second path, and circuitry for combining the phase modulated carrier signal on the first path with the phase modulated carrier signal on the second path for generating an amplitude modulated output signal. Feedback loops virtually eliminate residual phase shift and make the amplitude modulated output signal linearly proportional to the baseband signal.