Hello synth builders!
I’m building the PT2399 delay from the following stripboard layout. I noticed that there is no 1K resistor between the opamp and the output here:
Should there be? Opamps can drive a lot of current straight from the power rails. I made it a habbit to always add a 1K resistor on outputs to ensure that when an output is shorted to ground, it will not blow up the opamp.
Can anybody comment on this? Perhaps in this design, it is unlikely that the opamp will push out a big current?
Thanks!
The TL07x can handle shorts:
but nothing stops you from adding a resistor, of course.
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Thanks @fredrik .
I managed to find out that the max current will be 26mA when this happens, which is not crazy at all. So when TL07x chips are used, the output resistor is definitely not needed.
That’s for the new TL07xH series, though. I don’t think TI specifies the max current for the more common TL07xC variants; there’s this graph:
which corresponds to an internal impedance of ~300 ohms or so, but that’s about it.
“more common” being rather an understatement, at least in the case of through hole parts; near as I can tell the TL074H seems to exist only in TSSOP or SOIC packages, and the TL071H and TL072H not at all.
