On one of the analog inputs of an Atmega168 I have a series of two inverting op amps (first one reduces gain by 2, second one re-inverts signal. Using this configuration so that the first opamp can have a +5V connected to it in order to shift a bipolar source signal up). I am using TL072 amps connected to +/-12v
The output of the opamps is connected directly to clamping diodes so that the final output is limited to the range of 0-5V.
For the most part this is working but occasionally I am getting readings with higher than normal noise flutuations (at specific input voltages). I am concerned about how I have connected the opamp to the analog input pins and wonder if I need a current limiting resistor (200r ?) and perhaps even a capacitor to ground?
The signals I am reading at this input are relatively slow changing.
The output of the opamps is connected directly to clamping diodes so that the final output is limited to the range of 0-5V.
For the most part this is working but occasionally I am getting readings with higher than normal noise flutuations (at specific input voltages). I am concerned about how I have connected the opamp to the analog input pins and wonder if I need a current limiting resistor (200r ?) and perhaps even a capacitor to ground?
The signals I am reading at this input are relatively slow changing.