Op-amps

[Magnus Danielson]

> Hi!
> 
> can anyone tell me what op-amps are very good (price/quality).

Well, a standard op-amp wich is fairly good for it's price is the NE5534 and
it's twin version NE5532 (The military grade have the SE prefix).

The NE5534 can reach 130 dB of S/N ratio if making a wise selection on the
resistance the inputs see (about 7.2 kOhms if I recall rigth).

The NE5534 has NPN input transistors and this must be considered when using it
since it will not fit well into some circuit collection due to the impedance.

Another fairly nice standard op-amp is the TL-081 and TL-082 but it also has
it's drawbacks.

Both these can be used for most curcuitry (buffers, amplifiers and similar 
things) but it can be well worth the effort and use some more well suited 
op-amp
at critical positions.

> I don't really know which opamps to use in my oscillators ...

Can't tell unless we see your design... it depends on the surrounding 
curcuitry.

You have to think of the input and output impedances.
The raw amplification can be imporant sometimes.
The CMRR is usually worth considering, high CMRR is usually assumed.
The PSRR is seldom noted in datasheets, but it can be quite anoying the the
op-amp (or the curcuitry around it) has a low PSRR.

Also worth thinking about is availability, you probably not want to use a 
device
which is likely to be hard to find or may even be stoped produced. Think of the
lifetime concept, you migth need to get spare parts after a few years.

Other than that it is down to what you feel is best and what you feel happy
with. It is not all that uncommon that people throw in TL-082's just by habbit
and it becomes decent enougth... even if a carefull design would have made the
specs and function much more interesting...

Magnus