The 9V battery clip is a serious source of semiconductor damage, because the
customer ALWAYS touches the battery to the WRONG clip direction before he
locates (by feel) the correct direction- and the damage is already done.

My standard way of doing that is to use a Schottky diode, like a 1N5818 
in series
with the positive lead. The drop is usually less than 100mV, and 
negligible at
100uA. It seems to be about $0.10 USD max.

--Bob


Mike Hord wrote:

>>Don't you need a series diode anyway for reverse-battery protection?
>>
>>Best regards,
>>
>>Spehro Pefhany --"it's the network..."            "The Journey is the reward"
>>    
>>
>
>Not necessarily.  I haven't used a diode for reverse protection since
>Russell turned me on the the reverse PMOSFET method.  I prefer it
>greatly because it doesn't require such a high drop as the diode
>method.  I don't know if there are any disadvantages; it seems to be
>pretty sturdy to me.  It is a bit pricier, so in 10000 uber-cheap devices,
>it's probably not worth it, but in a higher quality device where an extra
>$0.10-$0.25 per unit won't make much difference, it's pretty appealing.
>
>Mike H.
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>  
>


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