# op-amp square wave oscillator

#### Exjay

Joined Nov 19, 2015
94
Please I need a expert help here or any experience hobbyist. I built this circuit and connected the output to LED to blink. Unfortunately, the LED did not blink but only on, so I begin to change the value of C1 & R4 to see the LED blink. At a particular value of C1 & R4, I coupled a capacitor to the LED from the output the LED blinks but was very faint. I coupled the capacitor since it passes time-varying signal and I also don't have an oscillator. What am asking now is that, is the circuit oscillating very fast that is not feasible to the eye?

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#### crutschow

Joined Mar 14, 2008
27,739
is the circuit oscillating very fast that is not feasible to the eye?
The blinking may or may not be visible to the eye, depending upon the values of the R's and C's, which you haven't posted.

#### Exjay

Joined Nov 19, 2015
94
1k ohms and 220uF

#### AlbertHall

Joined Jun 4, 2014
11,505
What op-amp are you using?
What supply voltage are you using?
You connected the LED between the amplifier output and which supply rail?
What value resistor did you have in series with the LED?

#### Exjay

Joined Nov 19, 2015
94
the op-amp I used was LM741 and I did not use a resistor with my LED

#### LesJones

Joined Jan 8, 2017
3,497
The LED is probably clamping the output of the op amp preventing it from oscillating. Put a resistor in series with the LED with a value that will limit the current to 5 mA. We can't tell you the value as you have not answered three of the four questions in post #4

Les.

#### Exjay

Joined Nov 19, 2015
94
The LED is probably clamping the output of the op amp preventing it from oscillating. Put a resistor in series with the LED with a value that will limit the current to 5 mA. We can't tell you the value as you have not answered three of the four questions in post #4

Les.
Thanks. Truly the LED is clamping the voltage. When I connected a resistor in series with the LED it blinks

#### AnalogKid

Joined Aug 1, 2013
9,357
Truly the LED is clamping the voltage. When I connected a resistor in series with the LED it blinks
WHAT resistor?
WHAT voltage?
Re-read posts #2, #4, and #6.

The 741 has two power supply pins. What are each one of them connected to?

There is no LED in the image you posted. Please show us *your* schematic, one that shows all components and connections.
Also, increase the 1K resistor 10 10K to make the blinking easier to see.

ak

#### wayneh

Joined Sep 9, 2010
17,153
Please show us *your* schematic, one that shows all components and connections.
AK, he said it's working. I suspect that's all he wants for now. Of course you're correct in asking for the usual details if he comes back with more questions.

#### Exjay

Joined Nov 19, 2015
94
AK, he said it's working. I suspect that's all he wants for now. Of course you're correct in asking for the usual details if he comes back with more questions.
9k

#### wayneh

Joined Sep 9, 2010
17,153
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