Ramp circuit to reduce spectral regrowth of power amplifiers

A method of modulating a power amplifier output signal level comprising the steps of:

• providing a capacitor;
• receiving a control signal having one of a first level and a second level;
• initiating a charging of said capacitor at a linear rate when said control signal changes from the second level to the first level;
• varying the power amplifier output signal level from minimum level to a maximum level during a continuous linear charging of said capacitor, where a time taken for said charging is a first transition time;
• initiating a discharge of said capacitor at the linear rate when said control signal changes from the first level to the second level;
• and,
• varying the power amplifier output signal level from the maximum level to the minimum level during a continuous linear discharging of said capacitor, where a time taken for said charging is a second transition time.

An integrated circuit for amplifying a signal for wireless transmission comprising:

• a first input port for receiving a first input signal for amplification thereof;
• an output port;
• a control port for receiving a control signal;
• an integrated capacitor electrically coupled to the control port for providing a control signal thereto in dependence upon a charge on the integrated capacitor and absent a comparator circuit coupled thereto;
• an integrated source current mirror electrically coupled with the capacitor and integrated therewith;
• an integrated sink current mirror electrically coupled with the integrated capacitor, the integrated source and sink current mirrors for providing current to the integrated capacitor and sinking current therefrom, the integrated current mirrors operable in a first mode to charge the integrated capacitor and operable in a second mode to discharge the integrated capacitor;
• and,
• an integrated power amplifier circuit coupled to the first input port for receiving the first input signal and for amplifying the first input signal in dependence upon the control signal, the amplified first input signal forming the output signal and provided at the output port;
• wherein, in use, a transition between said the first mode and the second mode results in a delayed transition of the control signal at the control port between first and second control signal levels, with a transition time of the delayed transition being substantially unrelated to an RC time constant of the integrated circuit.