rogs
Well-known member
I did look at the OPA1655 and the noise figure seems to be even lower than the 1641 ..... They don't always make reading data sheet noise figures very easy, and often quote different parameters! .Rogs does it yet again!
Have you considered opa1655 because of it's even lower noise? I forgot to include it in my last Mouser order
Whether it would make much difference in most 'real world' applications, I'm not sure?
Certainly it's ambient noise that dominates in the sort of environments I use my mics....
It doesn't state on the data sheet front page bullet points that the 1655 amp is unity gain stable. (They make a special point of mentioning that in the OPA164* data sheet ) It may well be of course?.... Just needs to be checked for unity gain buffer use!
The 1655 draws twice as much current at the 1641 .... still not that much, but it's not a plus point.
The input impedance is a lot lower on the 1655 - only about 100M in differential mode. That may be a bit low?
The input capacitance is also better on the 164* series according to this comment from a TI engineer posting on a different forum:
"The OPA1641 would be slightly better. It has the most stable input capacitance vs. common mode voltage that I've measured on any op amp. When we developed the OPA1656, this was also a major design target for us, and the designer and myself spent quite awhile in the lab with previous CMOS audio op amps (specifically OPA1652 and OPA1688) hunting for sources of input capacitance variation. The end result was slightly better than the previous parts, but we still met some limitations from the CMOS process itself. The dielectrically isolated JFETs on the input of the OPA1641 are superior in this regard."
Looks like the genuine JFET input of the 164* series may win out there?
Probably all just marginal differences in reality of course?
