Hi guys,

this is going to be a simple one but i'm very rusty and don't have time to trawl google results to get an answer.

I have a simple RC low pass filter going to the non-inverting input of an op-amp with gain set to 2 via the feedback to the interting input. There is an additional series resistor between the filter and the non-interting input and i'm not sure what the purpose of it is. its not a second order fiter as the feedback does not connect to the non-inverting side and since the op-amp input inpedence is much higher than the resistor I cant see it being a current limiting resistor, so what would the point of it be?

thanks.

 

See R7 below:

 

I see no particular reason for R7.