help needed for opamps

[steveelliott]

Now go check a common opamp - the LM324: https://www.ti.com/lit/ds/symlink/lm124-n.pdf. look on page 4.

The output voltage for the opamp is 2V for output currents of 10-20mA with at 1V overdrive on the input; to get the output down to 0.2V you need to restrict the output current to 12uA !
There are lots of other parameter listings and graphs in the data sheet that show for accurate operation of the opamp you want to keep the output resistance higher than 2K-10k.

And another one: the TL082 **broken link removed**
On page 4 they give the maximum output voltage swing for a 10k resistor. and on page 5 they have a graph that shows that the maximum output swing decreases as the load resistance decreases.

And check the prices of those analog devices opamps: $1-2 each!!!
Your boss would be a moron if he let you use a $2.00 opamp instead of a $0.15 opamp because you wanted to use a 500ohm feedback resistor instead of a 47kohm feedback resistor.

 

[FvM]

At least in part, this is a scary discussion. The OP asked about "selection of opamps resistors" and LvW suggested the "preferred range is between 500 ohms and 1 Megohm".

After some discussion about resistor noise, steveelliott talks against 500 ohm as feedback resistor value, although it was never suggested for this particular place. In return, maximum output current of various OP types gets spread out. Obviously, each single argument is right somehow. But you are mostly talking on cross purposes...