So generally, in the pst I have protected the inputs of a comparator like an LM139 with a clamping diode if needed.
This is assuming there is a potential risk of over voltageing the pins for whatever reason.
In general however, I see many circuits that just appear to stick a resistor in series with the inputs.
What is the purpose of this. In the idea case the input impedance is already very high.
Any current input on the pins with a large resistor is going to cause a reasonable voltage drop across this resistor causing error.
Can someone explain me what the purpose is and how to size this magical resistor?
Thanks
This is assuming there is a potential risk of over voltageing the pins for whatever reason.
In general however, I see many circuits that just appear to stick a resistor in series with the inputs.
What is the purpose of this. In the idea case the input impedance is already very high.
Any current input on the pins with a large resistor is going to cause a reasonable voltage drop across this resistor causing error.
Can someone explain me what the purpose is and how to size this magical resistor?
Thanks