The Analysis And Design Of Class AB Audio Amplifier With Gain Controlled By 32^th Logarithm

Audio power amplifier is an important part of power integrated circuits which is widely used in consumer electronic products.With the improvement of technology. Power Integrated Circuits (PIC) gets rapid development.Now more and more production of amplifiers with low power loudspeaker show the trend to develop class-D audio power amplifier, but class-AB audio power amplifiers have preponderant all the same in lower price, lower distortion, lower noise.This paper describes the development of the audio amplifier status, classification and working principle, Class AB audio amplifier and then conducted a systematic analysis. Then, the main models of the Class AB amplifier are analysised and designed. Subsequently, a high-fidelity, high power supply rejection ratio, low-quiescent-power class AB power amplifier was designed in this paper.The main circuit consists of a channel selection module MUX, pre-amplifier, post-class power amplifier, logic control circuit, PTAT current source reference, BYPASS circuits, as well as a time-multiplexing function 8bits SAR-ADC constituted. The circuit mainly has the following characteristics:In the pop-noise suppression, the design of the "S" shaped charge and discharge circuit, so that pop-noise in the sensory been greatly improved; Embedded within an 8-bit of the SAR-ADC, can realize a 32-step logarithmic volume control, control of the red-40dB～20dB; with the FADE function, set the gain and the gain are fast switching between-40dB.Class AB amplifier designed in this paper uses Huahong CZ6L of 0.5μm,1P3M process, the process MOS threshold voltage of the lower tube, but also provides 2KΩ/□high-resistance poly resistors, very suitable for Class AB amplifier design. Various modules and the overall circuit of the circuit design by Cadence and simulated by Spectre. On this basis, use the Layout to complete the whole circuit layout design and carry out flow sheet; set up a pilot environment, chip for testing. The results showed that output power in the load 3Ω,4Ωand 32Ω, respectively under 2.5W,2.2W,75mW, power supply rejection ratio at 50dB or more to drive 32Ωheadphone load. In addition, this class AB amplifier also has other advantages such as...