# operational amplifier

Discussion in 'General Electronics Chat' started by fireintheit, Aug 13, 2014.

1. ### fireintheit Thread Starter New Member

Jun 14, 2014
16
0
I just setup a non-inverting circuit using an tlc272 op amp cp. But I am not sure of what the op amp does. I am using a potentiometer to control the voltage supply. I believe there is suppose to be some type of gain but when check the amount of current flowing through the circuit (using multimeter), the amount of current in the output is equal to the amount of current in the in the input. I have connected the positive input to 9 volt battery and the negative input to ground.

I was wondering if some could explain what op amps are used for?

2. ### shteii01 AAC Fanatic!

Feb 19, 2010
3,921
600
Schematic? Where?

3. ### to3metalcan Member

Jul 20, 2014
234
25
Yeah. Schematic. The circuit you're describing really makes no sense according to the way you're phrasing it.

4. ### atferrari AAC Fanatic!

Jan 6, 2004
2,828
927
My assistant is trying hard to get the schematic

• ###### ball.jpg
File size:
7 KB
Views:
37
to3metalcan likes this.
5. ### crutschow Expert

Mar 14, 2008
16,195
4,329
Standard op amps are a voltage gain block with a very high open loop voltage gain and a non-inverting circuit should provide non-inverting voltage gain. Your mention of input and output current "flowing through the circuit" makes no sense. Post your circuit schematic.

Jun 14, 2014
16
0
7. ### fireintheit Thread Starter New Member

Jun 14, 2014
16
0
can some explain what voltage gain actually is. I am not sure why some would use op amps in circuits?

Feb 19, 2010
3,921
600
9. ### shteii01 AAC Fanatic!

Feb 19, 2010
3,921
600
Example.
I setup amplifier to provide gain of 6.
I put 1 volt in. I get out 6 volts.
Input 1 volt.
Output 6 volts.
I have successfully amplified 1 volt into 6 volts.

10. ### bertus Administrator

Apr 5, 2008
16,965
2,958
Hello,

How is the opamp powered?

Bertus

11. ### shteii01 AAC Fanatic!

Feb 19, 2010
3,921
600
As far as I can see, either power wire or ground wire are missing. It does not seem to be powered.

12. ### crutschow Expert

Mar 14, 2008
16,195
4,329
Say you have a small signal from some type of sensor and you want to make it larger so you can process it with an A/D converter. For that you can use an op amp to amplify the voltage from the small sensor voltage (say 100mv) to a voltage that the A/D input needs (say 5V) so you use an op amp circuit with a gain of 50.

Op amps are sort of the swiss-army-knife gain block of analog circuits. That can be configured to do all sorts of functions such an amplifier (single-ended, differential, trans-impedance), active-filter, integrator, differentiator, oscillator (sinewave or square-wave), precision rectifier, etc.

Edit: You seem to have only a vague knowledge of electricity and electronics. I suggest you read some tutorials on that subject.

13. ### to3metalcan Member

Jul 20, 2014
234
25
That picture is not very helpful. I can't make out the resistor values, nor can I even tell if you have the op amp the right way around. Here's a better question: what were you TRYING to do with this circuit?

(You also, as Shteii noted, don't seem to have connected it to power. Not to mention your schematic has two resistors and I see three here!)

14. ### fireintheit Thread Starter New Member

Jun 14, 2014
16
0
The red wire is the connection to ground, I have set -1 input to ground.

15. ### shteii01 AAC Fanatic!

Feb 19, 2010
3,921
600
Ok. That is Pin 4.

Then you have no power (Vdd) to the chip. The positive voltage from voltage supply (+15 volt normal max., +18 volt absolute max.) goes to the top right pin (Pin 8).

16. ### bertus Administrator

Apr 5, 2008
16,965
2,958
Hello,

Pin 8 is not per definition the +Vcc.
Here are the pinouts from a couple of opamps, taken from the datasheets:

Bertus

File size:
73.1 KB
Views:
31
File size:
94.2 KB
Views:
9
File size:
184.2 KB
Views:
7
File size:
1,009.4 KB
Views:
10
17. ### ramancini8 Active Member

Jul 18, 2012
461
129
You proved that op amps are useless; something I suspected for years. Still, why do they make billions of these things every year?

18. ### kubeek AAC Fanatic!

Sep 20, 2005
4,851
859
How the hell did you come to that conclusion? Opamps are useless only if you have no clue on how to actually use them. Reading the datasheet goes a long way.

19. ### shteii01 AAC Fanatic!

Feb 19, 2010
3,921
600
They provided the model of the op amp. I got datasheet for it. Datasheet says positive power supply is applied to Pin 8.

Why are you wasting your and everyone else's time?

20. ### to3metalcan Member

Jul 20, 2014
234
25
Congratulations all around; this goes a long way toward proving my thesis that ELECTRICITY IS A HOAX!