Electronics > Beginners
Op amp not working out as planned
Wimberleytech:
1) your average input voltage is about 400mV dc. The NI input of the amp is biased at 2.5Vdc. So your output is close to the positive rail. Is that what you want?
2) your resistors are not as precise as your calculator. With 5% tolerance, you are not too far off if the scope is giving you accurate measurements. Why not ac couple the output so that you can display it with the scope 200mV/div like the input? The scope might give a more accurate readout??
It is not good engineering to keep all of those extra digits in your calculation. Two significant digits is all you have.
Audioguru:
The NJM5532 is a Japanese copy of an American NE5532 so some of them might work when its supply is only 5V instead of the minimum of 6V.
If you want everything you make to work perfectly then use the original IC not a copy and use it with a supply voltage that is guaranteed to work.
netdudeuk:
--- Quote from: Wimberleytech on April 04, 2018, 05:16:59 pm ---1) your average input voltage is about 400mV dc. The NI input of the amp is biased at 2.5Vdc. So your output is close to the positive rail. Is that what you want?
2) your resistors are not as precise as your calculator. With 5% tolerance, you are not too far off if the scope is giving you accurate measurements. Why not ac couple the output so that you can display it with the scope 200mV/div like the input? The scope might give a more accurate readout??
It is not good engineering to keep all of those extra digits in your calculation. Two significant digits is all you have.
--- End quote ---
My resistors are from China so 5% is being optimistic ;) Actually, I measured them previously and got 4.67k and 5.1k.
Here's what we have with AC coupling on the output.
netdudeuk:
--- Quote from: Audioguru on April 04, 2018, 05:54:36 pm ---The NJM5532 is a Japanese copy of an American NE5532 so some of them might work when its supply is only 5V instead of the minimum of 6V.
If you want everything you make to work perfectly then use the original IC not a copy and use it with a supply voltage that is guaranteed to work.
--- End quote ---
That's the original IC that I ditched thanks. However, it did come from RS so will be genuine.
Wimberleytech:
--- Quote from: netdudeuk on April 04, 2018, 06:10:10 pm ---
--- Quote from: Wimberleytech on April 04, 2018, 05:16:59 pm ---1) your average input voltage is about 400mV dc. The NI input of the amp is biased at 2.5Vdc. So your output is close to the positive rail. Is that what you want?
2) your resistors are not as precise as your calculator. With 5% tolerance, you are not too far off if the scope is giving you accurate measurements. Why not ac couple the output so that you can display it with the scope 200mV/div like the input? The scope might give a more accurate readout??
It is not good engineering to keep all of those extra digits in your calculation. Two significant digits is all you have.
--- End quote ---
My resistors are from China so 5% is being optimistic ;) Actually, I measured them previously and got 4.67k and 5.1k.
Here's what we have with AC coupling on the output.
--- End quote ---
Move your NI voltage from 2.5 to 1.5 and run it again just to see if the distortion goes away
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