Trying to demonstrate the concept of DC biasing in amplifer

Discussion in 'The Projects Forum' started by tomshong, Aug 6, 2012.

  1. tomshong

    Thread Starter Member

    Oct 6, 2011
    36
    0
    Hi experts,

    I wanna run an idea by this forum before I try it out. I am trying to do a show and tell to demonstrate what a ‘poor’ DC biasing on an amplifier would do to the signal at the output. Basically, I want to show how to follow an I-V curve without using fancy lab equipment.

    I am thinking of building the audio amplifier using LM386, following the diagram for a gain of 20 in page 6 in the spec sheet below.

    http://www.ti.com/lit/ds/symlink/lm386.pdf

    Except I will add an extra variable resistor between the DC power supply and power pin 6. And a variable resistor between ground and ground pin 4. And I will include the variable resistor between Vin and pin 3 like in the spec sheet.

    I am thinking, if I feed an audio signal from a mp3 player, I can demonstrate the effect of what a poorly biased amplifier would sound like when I varying the 3 resistance above.

    By varying the resistor value connected to the DC supply, I can show how it’s the same as if I am moving operating region of an transistor between triode and saturation region in an IV curve. By vary the resistor value connected to the ground, I can demonstrate the effect if I move up and down the overdrive voltage level on an IV curve. By varying the input resistor and hence the input Vpp, I can show the effect of clipping.

    What you guys think? Would this be a right way to demonstrate the concept?

    Tom
     
    Last edited: Aug 6, 2012
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