Circuit Noiz Calculator
Here's another spreadsheet by yours truly. If you have worked with operational amplifiers of any kind, or did any audio mixing, i'm sure you had a noise problem at least once. That hiss when dealing with low level signals. Tape hiss, radio hiss, microphone hiss... It's everywhere.
Well, now you are able to know exactly how much noise your amplifier circuit makes. This spreadsheet takes your design parameters and calculates SNR (signal to noise ratio) for you. It gives a lot of insight and busts a lot of myths passed by word of mouth or by "common knowledge" on internet forums.
For example i thought that the hiss common to microphone preamps is inherent, and it's because of the circuit gain. Indeed, when connecting a more sensitive mike, you can turn the gain down and the hiss goes away - but that's only because the more sensitive mike gives a higher input level! Even if you would have a more sensitive mixer or recorder or whatever to capture the signal of the weaker mic, so you wouldn't need as much gain in your amplifier, the hiss would still be the same! For the same input signal level, SNR stays constant regardless of gain. That is, unless the signal source you are amplifying happens to have a hiss of its own, but that's a different can of worms...
Also, a lot of people say that the input and feedback resistors have to be as low in value as practical. As you will see, the noise source with the highest value dominates, and with common opamps like TL07x or NE553x, the highest noise source is the opamp itself, so the resistor values don't really matter unless you get into specialty opamps with really low self noise.
Technical notes:
More goodies coming soon, right now i need some sleep.
Well, now you are able to know exactly how much noise your amplifier circuit makes. This spreadsheet takes your design parameters and calculates SNR (signal to noise ratio) for you. It gives a lot of insight and busts a lot of myths passed by word of mouth or by "common knowledge" on internet forums.
For example i thought that the hiss common to microphone preamps is inherent, and it's because of the circuit gain. Indeed, when connecting a more sensitive mike, you can turn the gain down and the hiss goes away - but that's only because the more sensitive mike gives a higher input level! Even if you would have a more sensitive mixer or recorder or whatever to capture the signal of the weaker mic, so you wouldn't need as much gain in your amplifier, the hiss would still be the same! For the same input signal level, SNR stays constant regardless of gain. That is, unless the signal source you are amplifying happens to have a hiss of its own, but that's a different can of worms...
Also, a lot of people say that the input and feedback resistors have to be as low in value as practical. As you will see, the noise source with the highest value dominates, and with common opamps like TL07x or NE553x, the highest noise source is the opamp itself, so the resistor values don't really matter unless you get into specialty opamps with really low self noise.
Technical notes:
- Supported configurations: Inverting and non-inverting opamps.
- As usual, the input values are in blue and the results are in yellow. The nV/√Hz value for the opamp you can get from its datasheet.
- Current noise is not calculated, this is negligible in most cases. It will be added sometime.
More goodies coming soon, right now i need some sleep.
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