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
    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.

    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?

    Last edited: Aug 6, 2012