Source Follower

Discussion in 'Homework Help' started by Zsonali, Apr 7, 2014.

  1. Zsonali

    Thread Starter New Member

    Apr 3, 2014
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    Hello ,
    What is the main importance of a source follower?
     
  2. #12

    Expert

    Nov 30, 2010
    16,276
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    School work?
     
  3. LDC3

    Active Member

    Apr 27, 2013
    920
    160
    A source follower is an amplification circuit that outputs the same voltage level as the input voltage level.
     
  4. Zsonali

    Thread Starter New Member

    Apr 3, 2014
    18
    0
    Not a school work....but had a curiosity....
     
  5. #12

    Expert

    Nov 30, 2010
    16,276
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    A source follower can take in a high impedance signal and output it at a lower impedance, increased current. This is very good way to enable a signal to drive other parts without getting loaded down and getting a worse signal to noise ratio. There will be a DC voltage difference from using any transistor with a voltage, gate to source, required to turn it on. However, a jfet operated at its inherent idle current (Idss) can give you exactly the same signal out, including the DC component.
     
  6. PRS

    Well-Known Member

    Aug 24, 2008
    989
    35
    The high impedance of a FET makes it ideal as a voltage amplifier. It can be used to interface with inputs of low impedance and inputs of relatively high impedance without loading the source and therefore without losing voltage gain.
     
  7. lll

    New Member

    Mar 7, 2012
    21
    1
    It's like a buffer op amp.

    Let's say you have 12 volt source, and you need to power some device of an unknown impedance, for example a motor, but the motor needs 3 volts, not 12.

    You make a voltage divider with a 1k resistor and 3k resistor and the voltage across the 1k resistor gives you 3 volts. But if you try connecting that 3 volt output to the motor, it will mess everything up because now the motor is in parallel with the 1k resistor.

    The source follower fixes this problem. The source follower just transfers the voltage from the 1k resistor to the motor without messing up your original circuit, so the motor gets its 3 volts.
     
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