Help with this circuit

Thread Starter

supra

Joined May 11, 2012
1
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.




Low voltage regulator??
 

Audioguru

Joined Dec 20, 2007
11,251
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.
 

lll

Joined Mar 7, 2012
21
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:

KJ6EAD

Joined Apr 30, 2011
1,568
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.
I see no LED here. :rolleyes: There is a reverse biased zener diode though.
 
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