Audio frequency power amplifiers

An audio frequency amplifier for amplifying an audio frequency signal to obtain an amplified audio frequency signal and delivering the amplified audio frequency signal to a load, comprising:

• a. an input terminal, the audio frequency signal being applied to the input terminal;
• b. an output terminal;
• c. a return terminal, the load being connected between the output and return terminals;
• d. first amplification means for generating the amplified output signal, where the first amplification means has source and sink supply terminals;
• e. second amplification means for generating tracking source and sink supply signals at the source and sink terminals of the first amplification means, where
• i. the source and sink signals source current to and sink current from, respectively, the first amplification means, and
• ii. the second amplification means comprises source and sink output capacitors for filtering out high frequency components of the source and sink supply signals;
• and
• f. discharge means for discharging the source output capacitor to ensure that the source supply signal tracks the audio frequency signal and discharging the sink output capacitor to ensure that the sink supply signal tracks the audio frequency signal.

An amplifier comprising:

• a. first amplification means for amplifying an input signal to obtain an amplified output signal, the first amplification means having first and second supply terminals;
• b. power supply means for generating first and second supply signals and applying the first and second supply signals to the first and second supply terminals of the first amplification means, where
• i. the power supply means so generates the first supply signal that the first supply signal is above the output signal by a first predetermined offset value,
• ii. the power supply means so generates the second supply signal that the second supply signal is below the output signal by a second predetermined offset value, and
• iii. the power supply means comprises first and second output capacitors for filtering out high frequency components of the first and second supply signals;
• and
• c. discharge means for discharging the first and second output capacitors to ensure that a difference between the first and second supply signals does not exceed a sum of the first and second predetermined offset values.

An amplifier comprising:

• a. first amplification means for amplifying an input signal to obtain an amplified output signal, the first amplification means having first and second supply terminals;
• b. power supply means for generating first and second supply signals and applying the first and second supply signals to the first and second supply terminals of the first amplification means, where
• i. the power supply means so generates the first supply signal that the first supply signal is the greater of (A) a first predetermined offset value or (B) the output signal plus a second predetermined offset value,
• ii. the power supply means so generates the second supply signal that the second supply signal is the lesser of (A) a third predetermined offset value or (B) the output signal plus a fourth predetermined offset value, and
• iii. the power supply means comprises first and second output capacitors for filtering out high frequency components of the first and second supply signals;
• and
• c. discharge means for discharging the first and second output capacitors to ensure that
• i. a difference between the first supply signal and the output signal does not exceed the second predetermined offset value when a polarity of the output signal is positive, and
• i. a difference between the second supply signal and the output signal does not exceed the fourth predetermined offset value when a polarity of the output signal is negative.

An amplifier comprising:

• a. first amplification means for amplifying an input signal to obtain an amplified output signal, the first amplification means having first and second supply terminals;
• b. power supply means for generating first and second supply signals and applying the first and second supply signals to the first and second supply terminals of the first amplification means, where
• i. the power supply means generates first and second supply signals of equal magnitude, the magnitude of the first and second supply signals being the sum of a magnitude of the output signal and a predetermined offset value,
• ii. the power supply means comprises first and second output capacitors for filtering out high frequency components of the first and second supply signals;
• and
• c. discharge means for discharging the first and second output capacitors to ensure that
• i. a difference between the first supply signal and the output signal does not exceed the predetermined offset value when a polarity of the output signal is positive, and
• ii. a difference between the second supply signal and the output signal does not exceed the predetermined offset value when the polarity of the output signal is negative.

An amplifier comprising:

• a. power supply means for generating positive and negative fixed DC voltages at positive and negative power supply terminals, respectively;
• b. first amplification means for amplifying an input signal to obtain an amplified output signal, the first amplification means having first and second supply terminals;
• c. second amplification means for generating first and second supply signals and applying the first and second supply signals to the first and second supply terminals of the first amplification means, where the first and second supply signals are each offset from the output signal by a predetermined offset value, the second amplification means comprising:
• i. first filter means comprising a first inductor and a first output capacitor,
• ii. second filter means comprising a second inductor and a second output capacitor,
• iii. first switching means connected between the positive power supply terminal and the first filter means, the first switching means being controlled by a first control signal,
• iv. second switching means connected between the negative power supply terminal and the second filter means, the second switching means being controlled by a second control signal,
• v. a first freewheeling diode connected between an output of the first switching means and the negative power supply terminal of the power supply means, and
• vi. a second freewheeling diode connected between an output of the second switching means and the positive power supply terminal of the power supply means;
• and
• d. discharge means for discharging the first and second output capacitors to ensure that a difference between the first and second supply signals and the output signal does not exceed the predetermined offset value.