Hey folks
I'm experimenting with an LT1213 dual opamp and the datasheet explicitly states that one must be careful with oscillation. I was thinking of using 100 kohm resistors but the datasheet says that already with 10k the device may start to oscillate.
So I'm in need of some guidance. My application is to use the first opamp as a difference amplifier, with a pair of 74HC4066's to select the input attenuation from 30:1, 10:1, 5:1 and 1:1. The input difference can be max 30V, and I want the output to be max 1V. The other opamp is used as a noninverting summing amp to add an offset to the output of the first one to be converted by a ADC (specifically the AD7822, where the offset I add is the Vmid).
Here's a link to the schematic as it is at the moment. R8 and R9 is where the input signal goes. R8 and R9 would be 100k, R10-R13 and R14-R17 would be 100k, 20k, 10k, and 3.3k in that order.
Now can I get around this as simple as adding a feedback capacitor from the output of U_3/1 to its inverting input? What would be a suitable value? The datasheet says 10 pF or more.
Also, what would cause this oscillation? I've read about phase margin so I basically know that, but doesn't this require an input signal at the given frequency for oscillation to start? Or can the opamp oscillate completely on its own?
Thanks for your answers!
Please help
