Help with this circuit

Discussion in 'Homework Help' started by supra, May 11, 2012.

  1. supra

    Thread Starter New Member

    May 11, 2012
    1
    0
    Hi, I was hoping someone could help me with the following circuit. Does anyone know what this circuit is? I need to calculate the output current.


    [​IMG]

    Low voltage regulator??
     
  2. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    The opamp is connected as a follower so its output voltage is exactly the same as its input voltage.
    Do you agree that its input voltage is +5V?
    Then use Ohm's Law to calculate the output current.
    Simple.
     
  3. lll

    New Member

    Mar 7, 2012
    21
    1
    When the output is fed back into the negative terminal like that, it is called a unity gain buffer amplifier, or just buffer amplifier. So the voltage at the (+) terminal is the same as the output voltage.

    Not sure how your class treats LED's, but mine treated them like a voltage source. The flat side of the triangle is the positive end of the LED, and the pointed side of the triangle is negative, so the voltage in the (+) terminal of the op amp is -5 Volts (remember, the voltage across the 10k resistor connected to the (+) terminal is 0 because almost no current flows into the op amp terminals).

    So the output voltage is also -5 volts since the (+) terminal voltage of a buffer amplifier is the same as its output voltage. And then you just use ohm's law to find the current.
     
    Last edited: May 14, 2012
  4. KJ6EAD

    Senior Member

    Apr 30, 2011
    1,425
    363
    I see no LED here. :rolleyes: There is a reverse biased zener diode though.
     
Loading...