Load Tuning Circuit For Pulse-Width / Pulse-Position Modulation Amplifier And Related Techniques

An amplifier circuit having an input and an output, the amplifier circuit comprising:

• a pulse generator circuit having an input adapted to couple to the amplifier circuit input, said pulse generator circuit configured to receive a representative amplifier input signal at the pulse generator circuit input and substantially capable of implementing a pulse width modulation (PWM) scheme or a pulse position modulation (PPM) scheme and providing appropriately modulated analog signals at an output thereof;
• a driver amplification circuit having an input coupled to the output of said pulse generator circuit and having an output;
• an output amplification circuit having an input coupled to the output of said driver amplification circuit and having an output;
• a reconstruction filter having an input coupled to the output of said output amplification circuit and having an output coupled to the output of the amplifying circuit, said reconstruction filter having a filter characteristic which provides appropriately filtered signals at an output thereof;
• and
• a load modulation circuit coupled between the output of said reconstruction filter and the output of the amplifier circuit, said load modulation circuit having a selectable capacitance value wherein said load modulation circuit capacitance values are selected such that the amplifier circuit is capable of operation at power levels that exhibit a desired efficiency over a wide dynamic range of output powers.