Op Amp Behavoir
Op Amp Behavoir
(OP)

The above circuit represents my current configuration. The circuit is used to measure a ± 10.0 VDC signal.
R2 prevents my circuit from floating and provides a good high impedance.
R3 and R4 is a voltage divider that reduces the ±10.0 Volt signal.
Someone recommended on this forum, that I put a resistor on a Unity gain buffer. (R1)
The issue is that I am not getting full swing on "NODE 1" when the voltage is negative.
I've changed op amps
OPA2277 had the biggest difference of about 0.030 V
OP296GS had a better difference of 0.007 V
Basically at ± 10 I am getting +10.000 and -9.993 (OP297)
Can someone shed some light on the characteristics of opamps that I am somehow missing.
Thank You,
morizabal





RE: Op Amp Behavoir
RE: Op Amp Behavoir
Would an inverting configuration take care of the problem?
RE: Op Amp Behavoir
Another possibility is output voltage swing. That is unlikely too. The output does not have to go within seven volts of either supply rail either.
The only other possibility is that the output load current sourced or sunk by the particular op amp is being exceeded. With a 100K load that is not likely either.
First check everything is exactly as shown in the circuit, and the resistor values are correct. If I was a gambling man, I might bet R3 was 100 ohms not 100K.
The circuit as drawn should work perfectly o/k.
RE: Op Amp Behavoir