An integrated circuit device (10) has an operational amplifier (12) and a charge pump (14) for creating a negative voltage level -Vcc. The operational amplifier (12) preferably has various sub-components. In particular, a bias generator (36) is included and connected to a neutral voltage level (31) isolated from the negative voltage level and providing current for operational amplifier (12). An input stage (38) has inputs (16 and 18) for receiving two input signals and maintains the input signals in a balanced signal path. A conversion circuitry (40) receives the input signals and creates a single differential signal eliminating noise received in the input stage (38). An output stage prepares this single differential signal for transfer out of the operational amplifier (12).
A power supply device for driving an amplifier includes a first power generator, a second power generator, a charge pump and a control unit. The first power generator is used for providing a first voltage for a first power reception end of the amplifier. The second power generator is used for providing a second voltage. The charge pump is coupled between the second power generator and a second power reception end of the amplifier and is used for generating a third voltage for the amplifier according to the second voltage. The control unit is coupled to the second power generator and is used for controlling the second power generator, so as to adjust the second voltage to make the third voltage equal to a multiple of the first voltage.
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.
Methods and apparatus to detect impedance at an amplifier output are described. In one example, a method of determining a relative value of an amplifier output load may include determining a current provided to the amplifier output load in response to an input signal; determining a current provided to a reference load in response to a signal based on the input signal; comparing the current provided to the amplifier output load to the current provided to the reference load; and indicating a relationship between the amplifier output load and the reference load based on the current provided to the amplifier output load and the current provided to the reference load.
A high-efficiency audio power amplifier featuring a tracking power-supply and an active noise shaping unit for reducing non-linearly and audible noise. Several variations of an non-inductive switched-capacitor tracking power-supply are presented, which are well-suited to integrated-circuit implementation and battery operation, and which provide an efficient power supply for the output stage over a wide range of voltages that can exceed the voltage limits of the main power source. The output of the tracking power-supply can be fed into an analog power stage, or can be used as a Multi-Level Quantizer for generating the output directly. A feedback and noise shaping allows the use of low-cost components while relaxing design constraints. Some simple switching strategies are disclosed which offer power efficiencies in excess of 80%.
