I have a 12V supply going to an LD1117V50 to give me a +5V output. GND on the 12V and 5V side are shared.
My oscilloscope is showing me the output of the OPA336.
The OPA336 works fine when it's alone in the circuit with the LDO, I can get an amplification of the heat sensor inside the Weller RT tip, but as soon as I plug my Arduino, the output goes to 0. I don't even wire the OPA to an analog input, just powering up the Arduino from the +5V and GND of the LDO.
I tried various pins for powering on various arduino boards and models (Arduino Pro Micros with an ATMega32u4 and Arduino Pro Minis with ATMega328P). I even tried an Amica NodeMCU and a bare ATMega168 chip, same thing...
The OPA336 left alone consumes 0.02mA, plugging the Arduino Pro Mini brings the current consumption to 11mA, so it doesn't look like the LDO is being overloaded and can't supply enough current.
Well, as it happened more than once, seems to be a breadboard problem : I soldered the LDO + capacitors and the opamp (changed for an LM324 for now) with the accompanying resistors and capacitors to a perfboard, and it seems to work now... Sorry for bothering you with this useless post.
@jremington : The problem I had was that the opamp was working fine (showing 100s of mV on the output), but as soon as I wired the VCC & GND of the arduino to the power rails on the breadboard, the output of the opamp dropped to 0v. Removing the jumper wire from either VCC or GND brought the output back to the right value.
Nope, a basic 600 points with power rails on the side, with blue and red lines to indicate VCC & GND. I might have bought that one on aliexpress a long time ago...
