Audio Amplifier Output Stage

Construct a 3 stage 5w audio amplifier utilizing three stages a bjt differential pair input stage a bjt common emitter amplifier gain stage and a push pull emitter follower output stage.

Audio amplifier output stage. The practical amplifier circuit shown above could be the basis for a moderate power audio amplifier. Using scope channel 1 to observe the input at w1 and scope channel 2 to observe the output of the amplifier at r l. The class ab amplifier is a class b amplifier with a small bias voltage applied to the output devices to get them ready to play music. To achieve high linearity and gain the output stage of a class a amplifier is biased on conducting all the time.

Class ab amplifier output stage. Small signal transistor q1 and its associated components form the voltage amplification stage. Once the input stage has handled any signal processing needs the audio signal is passed to the output stage so that it increases in voltage and the mosfets can provide adequate amounts of current to drive our relatively low impedance speakers. Figure 3 push pull output stage waveforms next apply power and adjust the waveform generator so that w1 is a 100 hz triangle wave with 0v offset and 3 0 v amplitude peak to peak.

It features a typical though substantially simplified design as found in modern amplifiers with a class ab push pull output stage and uses some overall negative feedback. Analog mixed signal design. The emitter follows the signal on base within 650mv. The output stage of a typical push pull amplifier consists of two identical bjts or mosfets one sourcing current through the load while the other one sinking the current from the load.

Push pull amplifiers are superior over single ended amplifiers using a single transistor at the output for driving the load in terms of distortion and performance. Darlington complementary is the basic order in how the output stage of an amplifier is taught. Different amplifier designs use different amounts of biasing to balance between efficiency and silky smooth operation. Output stage is the stage that is connected to the loudspeaker.

All output transistors are arranged as emitter followers. Analog mixed signal design. Circuit diagram of a three stage practical audio power amplifier is shown in the figure below. Then for an amplifier to be classified as class a the zero signal idle current in the output stage must be equal to or greater than the maximum load current usually a loudspeaker required to produce the largest output signal.

Dac output filtering with sallen key opamp configuration connected to audio power amplifier rca in. How does a class d output stage work. High power output stage buffer driver for audio amplifier. Distorted output in class a audio amplifier.

The output transistors do not increase the size of the audio signal. Upon completion of this lab you should be able to.