Switching amplifier

Abstract

An amplifier having at least one switch controlled by an output voltage of a hysteresis block, wherein the hysteresis block is adapted to receive an input voltage signal based on an integration of an error signal, a low threshold voltage and a high threshold voltage, and is arranged to change the output voltage from a first value to a second value when the input voltage signal is higher than the high threshold voltage and to change the output voltage from the second value to the first value when the input voltage signal is lower than the low threshold voltage, and wherein the low threshold voltage is equal to V ref −αV DD and the high threshold voltage is equal to V ref +αV DD , where V ref is a common mode voltage level, α is a non-zero constant, and V DD is a power supply voltage.

1 . An amplifier comprising at least one switch controlled by an output voltage of a hysteresis block, wherein the hysteresis block is adapted to receive a low threshold voltage, a high threshold voltage and an input voltage signal based on an integration of an error signal, the hysteresis block being arranged to change said output voltage from a first value to a second value when said input voltage signal is higher than said high threshold voltage and to change said output voltage from said second value to said first value when said input voltage signal is lower than said low threshold voltage, and wherein said low threshold voltage is equal to V ref −αV DD , and said high threshold voltage is equal to V ref +αV DD , where V ref  is a common mode voltage level, α is a non-zero constant, and V DD  is a power supply voltage. 
   
   
       2 . The amplifier of  claim 1 , further comprising:
 an integrator coupled to said hysteresis block to provide said input voltage signal;   a power stage comprising said switches and coupled to receive said output voltage; and   adder circuitry arranged to receive an input signal of said amplifier and an output voltage of said power stage, and to provide said error signal to an input of said integrator, said error signal based on said input signal and said output voltage.   
   
   
       3 . The amplifier of  claim 1 , wherein said hysteresis block comprises a first comparator for comparing said input voltage signal to said high threshold voltage and a second comparator for comparing said input voltage signal to said low threshold voltage. 
   
   
       4 . The amplifier of  claim 3 , wherein said hysteresis block further comprises an SR flip-flop adapted to be set by the output of one of the first and second comparators and reset by the output of the other of the first and second comparators. 
   
   
       5 . The amplifier of  claim 1 , comprising a class D amplifier coupled to receive the output voltage of said hysteresis block, said class D amplifier comprising said switches. 
   
   
       6 . The amplifier of  claim 1 , further comprising circuitry adapted to generate said high and low threshold voltages, said circuitry comprising at least one variable resistance for allowing said supply voltage level to be adjusted. 
   
   
       7 . An electronic device comprising the amplifier of  claim 1 . 
   
   
       8 . A mobile communications device comprising the amplifier of  claim 1 . 
   
   
       9 . A method of controlling a power stage of an amplifier comprising:
 performing integration on an error signal to generate an integrated signal, said error signal being based on an input signal to be amplified and the output voltage of said power stage; and   comparing by a hysteresis block said integrated signal with a high threshold voltage and a low threshold voltage, and generating an output signal that changes from a first value to a second value if said integrated signal is higher than said high threshold voltage and changes from said second value to said first value if said integrated signal is lower than said low threshold voltage, wherein said low threshold voltage is equal to V ref −αV DD  and said high threshold voltage is equal to V ref +αV DD , where V ref  is a common mode voltage level, α is a non-zero constant, and V DD  is a power supply voltage.