Electronics > Beginners
Op Amp as comparator not behaving as expected
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tron9000:
Very interesting Circuit Hero999.

Never quite understood the applications of the common base configuration much, this has helped me also. :-+
exe:

--- Quote from: w2aew on May 11, 2018, 07:39:49 pm ---
Another simple example - a simulator won't have any problem putting 100A through a 1N914A diode - it doesn't know that you'd let the smoke out of it.

--- End quote ---

I think there are simulators that can produce some warnings. Unfortunately, all what I could google cost money. Still, many simulators can calculate dissipated power. I don't have LTSPice at hand, but I'll try your circuit at home to see if it can at least indicate how much power it will dissipate (accessible via pressing ALT + mouse click).
Old Printer:
Hero999

Could I ask what software you did those circuits in?  Thanks
Zero999:

--- Quote from: tron9000 on May 15, 2018, 08:25:59 am ---Very interesting Circuit Hero999.

Never quite understood the applications of the common base configuration much, this has helped me also. :-+

--- End quote ---
The key thing to remember is BJTs turn on when the potential difference across the base-emitter junction exceeds a diode drop. Unlike common emitter, common base is non-inverting and faster, as the base is at a fixed voltage, bypassed with a capacitor (low impedance at high frequencies), negative feedback via the base-collector capacitance is minimised.


--- Quote from: exe on May 15, 2018, 01:18:47 pm ---
--- Quote from: w2aew on May 11, 2018, 07:39:49 pm ---
Another simple example - a simulator won't have any problem putting 100A through a 1N914A diode - it doesn't know that you'd let the smoke out of it.

--- End quote ---

I think there are simulators that can produce some warnings. Unfortunately, all what I could google cost money. Still, many simulators can calculate dissipated power. I don't have LTSPice at hand, but I'll try your circuit at home to see if it can at least indicate how much power it will dissipate (accessible via pressing ALT + mouse click).

--- End quote ---
Yes it's possible to calculate power dissipation using LTSpice and energy too, which is often more important.

I have used a simulator which would "blow up components" when the maximum rating was exceeded, but it was rubbish, because it didn't take into account that most components can handle higher peak currents, than their continuous maximum rating, so that feature got turned off.


--- Quote from: Old Printer on May 15, 2018, 08:31:43 pm ---Hero999

Could I ask what software you did those circuits in?  Thanks

--- End quote ---
LTSpice, which is s free download.
Old Printer:


--- Quote from: Old Printer on May 15, 2018, 08:31:43 pm ---Hero999

Could I ask what software you did those circuits in?  Thanks

--- End quote ---
LTSpice, which is s free download.
[/quote]

Thanks, time I gave it a good look.
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