Hello,
I was wondering if anyone could tell me if the National LM833M (LM833 - Dual Audio Operational Amplifier) is capable of running off an single supply (12V). If not are they any other op-amps for single supply operation. The op-amp is to be used as an summer and buffer (eg. mono preout).
I was wondering if anyone could tell me if the National LM833M (LM833 - Dual Audio Operational Amplifier) is capable of running off an single supply (12V). If not are they any other op-amps for single supply operation. The op-amp is to be used as an summer and buffer (eg. mono preout).
I thought that most op-amps were made to run with dual supplies (eg. -15 and 15V)?
yes, but what do you do when all you have is single supply? check this out
http://www.eng.yale.edu/ee-labs/morse/compo/sloa058.pdf
http://www.eng.yale.edu/ee-labs/morse/compo/sloa058.pdf
Ground (zero volts) is just an arbitrary point... and as has been said, the LM833 is fine on a single rail.
Remember a -/+15 volt rail is a 30 volt supply as far as the opamp is concerned.
That's an excellent link 🙂 if you so if you don't mind I'm going to copy that to another thread where someone else was asking similar questions.
Can I just connect ground to the + pin or do I need to create a virtual ground using a voltage divider?
Yes is the simple answer 🙂
If you post the circuit you have we could advise better on how to do it.
Bellow is a preout I made. An inverted summing op-amp is obviously better (so I was told), also a inverted design doesn't strain the virtual ground current (the TLE2426 is 20mA max).
The question is, will having an inverted (read: out of phase) subwoofer signal be bad in a 2.1 setup?
The question is, will having an inverted (read: out of phase) subwoofer signal be bad in a 2.1 setup?
An externally hosted image should be here but it was not working when we last tested it.
Any speaker in any set up that's out of phase in relation toy the others is bad. Just use the other half of the LM833 to invert it back using for example 10k resistors.
For unity gain, how does one know to choose 10K/10K (Rf/Ri) or any other equal combination? Why not choose 1/1Ω? Also would a higher value resistor degrade the audio signal?
Don't choose any lower feedback resistor than it can drive with decent THD. Its not a behemoth power amp so to drive 1 Ohm. Going border low has essence if trying to stay near the OA's intrinsic input equivalent noise if it matters for a certain application.
or there is another trick! connect the sub out of phase.
faster, and 1 less opamp in the signal path.
Hard to not recommend this 😀
The virtual earth (inverting) configuration sees Rf as a load because the -input is always at zero volts. Go too high in value and the input bias current of the opamp may become a problem causing a DC offset and limited hf response due to lack of current drive for the input transistors and stray capacitances. Go to low and the opamp is using all it's output ability just to drive rf before you ever get to connect anything to the output. Most "audio" opamps will drive 600 ohms to full output swing, something like the TLO72 will not and around 2k2 is the lowest. Also the stage feeding the opamp has to drive Ri... it sees that as a load.
In practice anything from around 3k3 to 100k would be OK, with 10 k a very good compromise that would work well with any opamp.
Why an LM833 ?
I agree... I think it's just that folk don't like to think of the amp as having a phase inversion.
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