When designing circuits with OP's, do you mix up Signalground and Powerground (e.g. soldering it to the same rail) or do you have two (or even three for +,- and signal) rails that are starwired?
thanks,
Rüdiger
thanks,
Rüdiger
Hello Rudiger,
It's the high-current power traces that cause problems so for low power op-amps, signal ground and power ground can be the same thing. For high power (Gainclone and the like) they should definately be seperate.
If you're making a PCB then using the top layer as a ground plane is always a good idea regardless of power consumed as it tends to make layout easier as well as giving a solid power/signal strategy.
Nice one,
David.
It's the high-current power traces that cause problems so for low power op-amps, signal ground and power ground can be the same thing. For high power (Gainclone and the like) they should definately be seperate.
If you're making a PCB then using the top layer as a ground plane is always a good idea regardless of power consumed as it tends to make layout easier as well as giving a solid power/signal strategy.
Nice one,
David.
I prefer to have separated ground paths for signal (input resistor net of the OA etc.) and supply (supply bypass capacitors ground). These connected into starr topology.
It has been my experience that if input impedances aren't too high (greater than 10k, let's say), supply currents aren't too high (more than 20-30mA), and pcb traces are wider than 20 mils that there is little to be gained from star grounding. Of course, this is no license to put ground loops into the system - those are never welcome, if even they seem to cause no trouble - but it does make board layout much easier if you aren't constrained to route every single ground connection back to a spur off of the filter capacitor stack! I have made several pc boards in which multiple op-amps were arranged in a straight line down parallel supply rail tracks, obstensibly a no-no, with no ill-effects whatsoever. Even still, tossing in the occasional 10uF tantalum from each rail to ground usually cures any possible track inductance/resistance problems. Examination of many different products' pc boards will reveal that many designers feel the same way.
Disclaimer: I mean this to apply only to the topic at hand. Ymmv.
Disclaimer: I mean this to apply only to the topic at hand. Ymmv.
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