A power-efficient audio amplifier combining switching and linear techniques

Abstract

Integrated class-D audio amplifiers are very power efficient but require an external LC reconstruction filter, which prevents further integration. Also due to this filter, large feedback factors are hard to realize, so that the load influences the distortion and transfer characteristics. The 30-W amplifier presented in this paper consists of a switching part that contains a much simpler filter and a linear part that ensures a low distortion and flat frequency response. The switching part of the amplifier was integrated in a BCD process. Combined with a linear part and with a loudspeaker as load, it has a flat frequency response 6 6 60.3 dB, a dissipation that is up to five times lower than a traditional class-AB audio amplifier, and a distortion of < < <0.02% over power and frequency range.

Optimum Bias Calculation for Parallel Hybrid Switching-Linear Regulators

“…Hybrid combinations of linear and switching regulators have been proposed both for audio amplifiers [1,2], and dynamic supply modulators for RF power amplifiers (RF PAs) [3][4][5]. In contrast to conventional voltage regulation applications, audio and RF-PA supply applications require fast, accurate, time-varying regulation of the output voltage to meet strict spectral performance requirements [6,7].…”

A wideband supply modulator for 20MHz RF bandwidth polar PAs in 65nm CMOS

“…Fig. 4 shows the architecture of the modulator comprising of a self-oscillating parallel linear and switching amplifier [2], [5], [7], [8], [10]. The linear amplifier (AB) takes care of the linearity while the switching amplifier (D) supplies most of the current ensuring high efficiency.…”

“…If the thresholds current of AB are and , then the oscillation frequency as derived in [10] is given by (2) where is the load seen from the supply side, and is the time-dependent envelope voltage or the supply voltage for the RF PA.…”

“…The class D amplifier is simply a chain of inverters as shown in Fig 9. The conduction loss of the output stage is (10) where and are the switch resistance of pMOS and nMOS respectively and D is the duty cycle.…”

A 50MHz bandwidth multi-mode PA supply modulator for GSM, EDGE and UMTS application

“…1 [1], [2], [4], [5]. It contains a linear regulator and a DC/DC converter in master-slave configuration.…”