Single supply direct drive amplifier

Abstract

A driver amplifier operative from a single DC voltage supply, coupled directly to the output load without the need for DC coupling capacitors used for preventing DC reaching the output load. An onboard power supply generates a negative voltage rail that powers the output amplifiers, allowing driver amplifier operation from both positive and negative rails. Since the amplifiers can be biased at ground potential (0 volts), no significant DC voltage exists across the load and the need for DC coupling capacitors is eliminated.

1 . A circuit enabling a driver amplifier to operate from a single voltage supply comprising: 
 an amplifier having an output arranged for coupling to an output load, said amplifier having first and second power supply leads, said first power supply lead connected to a power supply voltage, wherein the output of the amplifier is coupled to the output load without an intervening DC coupling capacitor;    a charge pump DC voltage-to-voltage converter having an output, said DC voltage-to-voltage converter having a power source lead connected to the supply voltage, the output of said DC voltage-to-voltage converter connected to the second power supply lead, and said DC voltage-to-voltage converter generating an output voltage at the output that is substantially equal in magnitude to some negative quanta of the power supply voltage; and a shutdown circuit operable to control operation of said circuit.    
   
   
       2 . The circuit of  claim 1  connected to a common ground by two external capacitors in the range of 0.47 to 3.3 micro farads.  
   
   
       3 . An amplifier circuitry for directly driving stereo headphones, said amplifier circuitry being driven by a single supply voltage VDD, said amplifier circuitry comprising: 
 a first and a second amplifier, the first amplifier having an output coupled to a first headphone without any intervening DC coupling capacitor and the second amplifier having an output coupled to a second headphone without any intervening DC coupling capacitor, each of the first and second amplifier having a VDD power supply lead connected to a positive voltage supply VDD; and    a charge pump circuitry output connected to a −VDD supply voltage of the first and second amplifier, wherein said charge pump circuitry output provides a voltage substantially equal in magnitude to a negative quanta of the VDD supply, said charge pump further having a power supply lead connected to the VDD supply voltage.    
   
   
       4 . A circuit enabling a driver amplifier to operate from a single voltage supply comprising: 
 an amplifier having an output arranged for coupling to an output load, said amplifier having first and second power supply leads, said first power supply lead connected to a power supply voltage, wherein the output of the amplifier is coupled to the output load without an intervening DC coupling capacitor;    a charge pump having an output, said charge pump having a power source lead connected to the supply voltage, and said charge pump generating an output voltage at the output that is substantially equal in magnitude to some negative quanta of the power supply voltage; and    a linear regulator having an input and an output, the output of the charge pump connected to the input of the linear regulator, and the output of the linear regulator coupled to the second power supply lead of the amplifier.    
   
   
       5 . A driver amplifier circuit comprising: 
 an amplifier having an output coupled to a load without an intervening DC coupling capacitor, the amplifier having a positive power lead and a negative power lead,    a voltage supply coupled to the positive power lead, the voltage supply providing a positive voltage, and    a charge pump coupled to the voltage supply, the charge pump having an output coupled to the negative power lead of the amplifier, the output of the charge pump being a negative voltage;    wherein the negative voltage is substantially equal in magnitude to a quanta of the positive voltage.    
   
   
       6 . A direct drive charge pump enabled stereo headphone system comprising the following formed on a single integrated circuit: 
 a single power input for providing, internal to said integrated circuit;    a VDD supply voltage originating external to said integrated circuit;    a charge pump coupled to said single power input and operable to provide, internal to said integrated circuit,    a voltage substantially equal in magnitude to a negative quanta of said external VDD supply;    a first headphone amplifier power by both said external VDD supply and said voltage substantially equal in magnitude to the negative quanta of said external VDD supply, said first headphone amplifier having a first audio input driven by a first audio signal provided external to said integrated circuit, and a first audio output suitable for driving a stereo headphone without any intervening DC coupling capacitor;    a second headphone amplifier powered by both said external VDD supply and said voltage substantially equal in magnitude to the negative quanta of said external VDD supply, said second headphone amplifier having a second audio input driven by a second audio signal provided external to said integrated circuit; and a second audio output suitable for driving said stereo headphone without any intervening DC coupling capacitor.    
   
   
       7 . A direct drive charge pump enabled stereo headphone system as recited in  claim 6 , wherein said first audio input is an audio in for a right stereo headphone and said second audio input is an audio in for a left stereo headphone.  
   
   
       8 . A direct drive charge pump enabled stereo headphone system as recited in  claim 6 , wherein said first audio input is coupled to an inverting terminal of said first headphone amplifier and said second audio input is coupled to an inverting terminal of said second headphone amplifier.  
   
   
       9 . A direct drive charge pump enabled stereo headphone system as recited in  claim 6 , wherein a non-inverting terminal of said first headphone amplifier is coupled to a non-inverting terminal of said second headphone amplifier.  
   
   
       10 . A direct drive charge pump enabled stereo headphone system as recited in  claim 9 , wherein said non-inverting terminal of said first headphone amplifier and said non-inverting terminal of said second headphone amplifier are coupled to ground.  
   
   
       11 . A direct drive charge pump enabled stereo headphone system as recited in  claim 6 , further comprising: 
 a first resistor coupled to said first audio input and an inverting terminal of said first headphone amplifier,    a second resistor coupled to said first audio output and said inverting terminal of said first headphone amplifier,    a third resistor coupled to said second audio input and an inverting terminal of said second headphone amplifier, and    a fourth resistor coupled to said second audio output and said inverting terminal of said second headphone amplifier.    
   
   
       12 . A direct drive charge pump enabled stereo headphone system as recited in  claim 6 , further comprising: 
 a first capacitor having a first lead and a second lead, said first lead coupled to said charge pump and said second lead coupled to said charge pump, said first capacitor located off said integrated chip, and    a second capacitor having a first lead and a second lead, said first lead coupled to said charge pump and said second lead couple to ground, said second capacitor located off said integrated chip.    
   
   
       13 . A direct drive charge pump enabled stereo headphone system as recited in  claim 6 , further comprising a short circuit protection device.  
   
   
       14 . A direct drive charge pump enabled stereo headphone system as recited in  claim 6 , further comprising a bias circuitry device.  
   
   
       15 . A direct drive charge pump enabled stereo headphone system as recited in  claim 6 , further comprising a click/pop suppression device coupled to said first headphone amplifier and said second headphone amplifier.  
   
   
       16 . A direct drive charge pump enabled stereo headphone system as recited in  claim 6 , further comprising a shutdown control device coupled to said charge pump.  
   
   
       17 . A direct drive charge pump enabled stereo headphone system as recited in  claim 15 , further comprising a shutdown control device coupled to said charge pump and said click/pop suppression device.  
   
   
       18 . A direct drive charge pump enabled stereo headphone system as recited in  claim 6 , further comprising: 
 a first capacitor having a first lead and a second lead, said first lead coupled to a non-inverting terminal of said first headphone amplifier and said second lead coupled to said first audio input, said first capacitor located off said integrated chip, and    a second capacitor having a first lead and a second lead, said first lead coupled to a non-inverting terminal of said second headphone amplifier and said second lead coupled to said second audio input, said second capacitor located off said integrated chip.