[sdiy] input buffer question

[Dave Manley]

David G. Dixon wrote:
>> For a non-inverting op amp voltage follower, the input is high impedance,
>> so you don't have to worry about the 10K resistor contributing to the
>> input loading.  BUT for the same reason it also won't really offer any
>> protection; you'll probably want clamping diodes to the positive and
>> negative supply rails.  Maybe Schottky diodes if you want to be really
>> cautious.  I don't know why you would put a resistor in the feedback loop,
>> I don't think it would do anything.
>>     
>
> Brilliant!  Thanks, Scott.  I will leave the 10k resistor on the input, then
> put clamping diodes (just plain ol' 1N4148s) between each rail, the
> resistor, and the + input of the opamp.  The diodes will protect the opamp,
> and the resistor will limit the current through the diodes.  I will also
> remove the feedback resistor.
>   
Hi David,

Curious why  your ASR input need any different treatment than any other 
modules?

BTW, the opamp may already have protection diodes to the rails.  With 
the series resistor on the input to limit current through the internal 
diodes, are external diodes really necessary?  I don't know, just asking.

-Dave