Optimal amplifier topology for distortion-free B and D class audio power amplifiers

摘要

The optimal amplifier topology for distortion-free B- and D-class audio power amplifiers is a SISO transmission system with a signal input terminal to which the input signal (Vin) is fed in, with a signal output terminal from which a load impedance, such as a loudspeaker in the low frequency range, is connected the output voltage (Vout) in the transmission frequency band B, B = [0, -3dB-ω], and with a target amplification factor defined with the amplitude ratio, Vout / Vin, comprising a main amplifier (M) designed either as a linear B class -Power output stage or switched D-class power output stage, the output of which is connected to the signal output terminal for the delivery of electrical power to the load impedance, with a differential input: a non-inverting plus and an inverting minus input, with a complex transfer function M (ω) without significant linear distortion, i.e. with a constant actual amplification factor (M (0)) in the overhead transmission frequency band (B), a passive feedback circuit (ß) with a complex transfer function β (ω) and a constant attenuation in the transmission frequency band (B), β (0), which corresponds to a reciprocal actual gain factor (M (0)), β ( 0) = 1 / M (0), an AEF input circuit (AEF-ES) with two inputs and two outputs: with its first input (FB-In) for feeding in a feedback signal (Vfb) from the signal output terminal via the feedback circuit ( ß), with its second input (Ref-In), which serves as a signal input terminal, with its first output (Ref-Out) for feeding the non-inverting plus input of the main amplifier (M) with a signal (Vro), with its Second output (Error-Out) for feeding the inverting minus input of the main amplifier (M) with an error signal (Veo), has the following features: a) The AEF input circuit (AEF-ES) consists of a first linear differential small-signal amplifier (A1), a second linear en differential small signal amplifier (A2), as well as a first resistor (R1) and a second resistor (R2) .b) The first input (FB-In) of the AEF input circuit (AEF-ES) is electrically connected to the non-inverting plus -Input of the first differential small-signal amplifier (A1) .c) The first output (Ref-Out) of the AEF input circuit (AEF-ES) is electrically connected to the output of the first differential small-signal amplifier (A1) .d) The second output (Error-Out) of the AEF input circuit (AEF-ES) is electrically connected to the inverting minus input of the first differential small-signal amplifier (A1) and fed in from the output of the second differential small-signal amplifier (A2), e) The inverting minus The input of the second differential small signal amplifier (A2) is connected to signal ground f) The non-inverting plus input of the second differential small signal amplifier (A2) is connected to one end of the first resistor (R1) and one end of the second Resistor (R2) electrically connected. G) The other end of the first resistor (R1) is electrically connected to the first output (Ref-Out) of the AEF input circuit (AEF-ES). H) The other end of the second resistor (R2 ) is electrically connected to the first input (FB-In) of the AEF input circuit (AEF-ES). i) The target amplification factor Vout / Vin is equal to the actual amplification (M (0)) of the main amplifier (M) .