Testing Opamps

Matttcattt · 26th January 2004, 08:15 PM

I HAVE searched (for once

), but i could not find any info on testing op-amps.

I have approx 50 TL081s, which i was given, "as sold" so to speak, as half of them are probably dead. does anyone have a simple circuit (to be built on a breadboard) that i could use to test the opamps?

any help appreciated.

thanks in advance,

Matthew

Matttcattt · 27th January 2004, 05:18 PM

could i use a circuit something like this?

Centauri · 29th January 2004, 12:25 PM

With that circuit, the led will probably just stay on. I would suggest wiring pot from +ve to -ve rails, adding 10k resistor from pot wiper to pin2, and 10k resistor from pin2 to pin6, and another led in parallel to existing led but opposite polarity. This will give an inverting amplifier with gain of 1. With the pot in the middle, both leds should be out - varying the pot one way or the other will cause one of the leds to vary in brightness with the pot.

Cheers

richie00boy · 30th January 2004, 08:40 AM

...adding of course that pin 3 is tied to 0V for the reference of the amp

Matttcattt · 30th January 2004, 09:40 PM

Quote:

Originally posted by Centauri
With that circuit, the led will probably just stay on. I would suggest wiring pot from +ve to -ve rails, adding 10k resistor from pot wiper to pin2, and 10k resistor from pin2 to pin6, and another led in parallel to existing led but opposite polarity. This will give an inverting amplifier with gain of 1. With the pot in the middle, both leds should be out - varying the pot one way or the other will cause one of the leds to vary in brightness with the pot.

Cheers

thanks.

Quote:

Originally posted by richie00boy
...adding of course that pin 3 is tied to 0V for the reference of the amp

what do you mean by that?

richie00boy · 31st January 2004, 05:44 PM

Quote:

what do you mean by that?

That unless you connect that pin to 0V, the circuit will just go mad as it has no ground reference.

PS hope your crazy chip amp sub thing worked out OK

Matttcattt · 31st January 2004, 07:01 PM

Quote:

Originally posted by richie00boy

That unless you connect that pin to 0V, the circuit will just go mad as it has no ground reference.

PS hope your crazy chip amp sub thing worked out OK

i realise this. i do have some basic knowledge of electronics.

yes, it is working fine. i still havent sorted out a permenant power supply yet though.

Stocker · 4th March 2004, 07:36 PM

This is taking a couple of ideas from elsewhere as well...

the 2k pot sets the Vin. the other two are for adjustment. the 100R resistors are to protect the power supply from shorted devices being tested.

I am in the process of building this from junk-bin parts. Actually, I'm ~trying~ to make a quad opamp tester, with all 4 inputs from the one pot.

Any comments or suggestions for improvement?

Stocker · 5th March 2004, 11:16 AM

okay, try again with the picture

Stocker · 5th March 2004, 01:22 PM

http://images.ofoto.com/photos591/1/...4103_0_ALB.jpg

26th January 2004, 08:15 PM	#1
Matttcattt diyAudio Member Join Date: Feb 2003 Location: Bristol	Testing Opamps I HAVE searched (for once ), but i could not find any info on testing op-amps. I have approx 50 TL081s, which i was given, "as sold" so to speak, as half of them are probably dead. does anyone have a simple circuit (to be built on a breadboard) that i could use to test the opamps? any help appreciated. thanks in advance, Matthew __________________ If it aint broke, don't fix it. If it is broke, fix it. If you can't fix it, take it apart and see how it "worked".

5th March 2004, 01:22 PM	#10
Stocker diyAudio Member Join Date: Dec 2003 Location: Austin	feeling like a moron now http://images.ofoto.com/photos591/1/...4103_0_ALB.jpg __________________ Jesus loves you.

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29th January 2004, 12:25 PM	#3
Centauri diyAudio Member Join Date: Jul 2003 Location: Newcastle, Australia	With that circuit, the led will probably just stay on. I would suggest wiring pot from +ve to -ve rails, adding 10k resistor from pot wiper to pin2, and 10k resistor from pin2 to pin6, and another led in parallel to existing led but opposite polarity. This will give an inverting amplifier with gain of 1. With the pot in the middle, both leds should be out - varying the pot one way or the other will cause one of the leds to vary in brightness with the pot. Cheers

30th January 2004, 08:40 AM	#4
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	...adding of course that pin 3 is tied to 0V for the reference of the amp

5th March 2004, 11:16 AM	#9
Stocker diyAudio Member Join Date: Dec 2003 Location: Austin	okay, try again with the picture

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