I tore the original CMOS opamp off of a FreeDSP Classic and ran it passive output filter. I think it sounded better before I did that, so I want to replace the active filter. Problem is the only thing I have on hand is a OPA1644. I was wondering if anyone knew what would happen with an amp rated down to 4.5 volts being fed with only 3.3. I figure anything could happen, mostly bad, but that someone might know..
Since you seem to know, may I ask which specificaton would suffer worst? I ask because I'm pretty sure some noise related to the input would come out even at 3.3v.
The 'amplifier' function might not exist and the output might be some random voltage between the supply rails. 🙂
Aside from the snark, keep in mind that a lot of low voltage op amps exist now, some with truly amazing specifications, very high bias levels and gargantuan bandwidths. I often have to ignore these amplifiers, since I need to use op amps for traditional line level signals. But, for a low voltage system, it's worth using a vendor's parametric search and seeing what's out there, rather than hoping that a high voltage amp might limp along being misapplied.
Aside from the snark, keep in mind that a lot of low voltage op amps exist now, some with truly amazing specifications, very high bias levels and gargantuan bandwidths. I often have to ignore these amplifiers, since I need to use op amps for traditional line level signals. But, for a low voltage system, it's worth using a vendor's parametric search and seeing what's out there, rather than hoping that a high voltage amp might limp along being misapplied.
Well I'm inclined to hotwire it for five volts since that is the main supply level and pretty clean. The spec sheet performance of the original amp was scary bad by modern HiFi standards, though not a whole lot worse than the DSP chip feeding it. Maybe I will look for something better that runs at 3.3, though I really don't imagine stellar performance from anything that can do that.