[sdiy] Non-inverting output buffer

[Dave Manley]

David G. Dixon wrote:
> ...Of course, I'm assuming a +/-15V supply here...
>   
>> For example, a 1k resistor inside the junction will only limit the
>> short-circuit current to about +/-13.5V/1k = +/-13.5mA regardless of the
>> input , while that same resistor outside the junction will limit the
>> current
>> to V_in/1k.
>>
>> Indeed, 75R does not really provide any short-circuit protection, since
>> the
>> output current would be +/-13.5V/75R = +/-180mA, which is well beyond the
>> current which most opamps can generate.

Is this correct?  The datasheets for the TL072 that I've looked at show 
300ohms of resistance between the output pin and the output transistor's 
emitter.  Assuming Vce_sat is 0V then with  a shorted output  and 15V 
supply the current should be 15V/300ohm = 50mA.

-Dave

http://www.diodes.com/datasheets/TL072.pdf
http://www.st.com/stonline/books/pdf/docs/2298.pdf (actual specs 
Ios=10,40,60 min,typ,max)
http://focus.ti.com/lit/ds/symlink/tl072.pdf (192 ohms instead of 300 
gives 78mA)