Amplitude modulator circuit having multiple power supplies

A radio comprising:

• an amplitude modulator circuit, having an input for receiving an input information signal and an output for providing an output signal, the amplitude modulator circuit comprising:
• a plurality of amplifying means, each having a selected gain for amplifying the input information signal, and each having an input for selectively receiving a control signal, representing the input signal, for activating the amplifying means and an output coupled to the load to provide the output signal;
• coupling means for coupling a different voltage to each amplifying means;
• and
• driver means having an input coupled to receive said input signal and having a plurality of driver outputs, each of said driver outputs being coupled to one of the plurality of amplifying means for providing the control signal to the amplifying means having the lowest supply voltage sufficient to provide the selected gain.

An amplitude modulator circuit having an input for receiving an input information signal and an output for providing an output signal that is proportional to the input information signal, to a load, the amplitude modulator circuit comprising:

• a plurality of pass transistors, each pass transistor having a first electrode coupled to receive a supply voltage, a second electrode for providing the output signal, and a control electrode for selectively receiving a control signal for activating said pass transistor;
• means for applying a plurality of supply voltages to the first electrodes of the plurality of pass transistors, at least some of the supply voltages having different values;
• and
• driver means having an input coupled to receive the input information signal and having a plurality of driver outputs, each of the driver outputs providing the control signal to the control electrode of the pass transistor having the lowest supply voltage sufficient to supply the required voltage to the load.