A spread spectrum transmission circuit includes a phase locked loop composed of a filter. The phase locked loop generates a series of incremental control signals and decreasing control signals based on the frequency difference and phase difference between a reference clock signal and a feedback signal. The circuit further has a frequency locked loop an amplitude locked loop, a digital-analog converter, an injection current source, an extraction current source, a multiplexer is connected to the locked phase loop and a rail-to-rail digital signal generator having an input connected to the multiplexer and an output connected to inputs of the locked frequency loop and the locked amplitude loop.