Audio amplifier

A solid-state amplifier comprising:

• a driver means for providing two drive signals of opposite phase;
• first and second solid-state output devices, each of said output devices having a control input terminal, a supply terminal and an output terminal, wherein the control terminal of the first output device is connected to one output of said driver means and the control terminal of the second output device is connected to the other output of said driver means;
• driver power supply means for providing operating voltages to said driver means;
• a first control resistor connected between the output terminal of said first output device and a terminal of said driver power supply means;
• a second control resistor connected between the output terminal of said first output device and a terminal of said driver power supply means;
• a first floating independent power supply, the positive terminal of which is connected to the supply terminal of said first output device and the negative terminal of which is connected to the output terminal of said second outout device;
• and
• a second floating independent power supply, the positive terminal of which is connected to the supply terminal of said second output device and the negative terminal of which is connected to the output terminal of said first output device, said amplifier being utilized to drive a load which is connected between the output terminals of said first and second output devices.

A bridge connected output stage for an amplifier comprising:

• a first output device having a control input, a supply input and an output;
• a first floating independent power supply, the first terminal of which is connected to the supply input of said first output device, said first output device and said first power supply forming one side of a bridge;
• a second output device having a control input, a supply input and an output, said output being connected to the second terminal of said first power supply;
• a second floating independent power supply, one terminal of which is connected to the supply input of said second output device and the other terminal of which is connected to the output terminal of said first output device, said second output device and said second power supply forming the other side of the bridge;
• a third power supply;
• and
• passive means, connected to the third power supply, for maintaining the quiescent value of the control input current to said output devices at a constant level despite temperature variations in the output devices.

A linear audio amplifier comprising:

• a bridge having a first floating power supply connected with one polarity in series with a first transistor amplifying device across two opposite nodes of said bridge, and a second floating power supply connected with opposite polarity in series with a second transistor amplifying device across the same two nodes, a load being connectable across said same nodes;
• independent first and second high impedance current source bias circuits respectively connected to said first and second transistor amplifying devices, each of said bias circuits including a passive current control element and providing a current which is entirely constrained to the base-to-emitter path of the associated transistor amplifying device whereby no bias current flows through either floating power supply, the current provided by each current source being determined by said passive element so that said bias circuit maintains the base current of that associated transistor device constant regardless of temperature change;
• and
• drive means for supplying corresponding but oppositely phased audio signals to the inputs of said first and second transistor devices.