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Author Topic: NPN & PNP LTspice  (Read 766 times)

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Offline Spitfire1.2Topic starter

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NPN & PNP LTspice
« on: February 04, 2020, 02:00:44 pm »
Hello!

  I a bit confused with a circuit on LTspice and I need your help if possible.

I tried simulating the following circuit, from my calculation the power on the Led should be around 20mA, but the simulated circuit shows 1.07mA. I tried the same circuit on other simple online simulators like part-sim and falstad and I got the 20mA. Is there something critical that I am missing?  Or is it a design error in LTspice?

Thanks for your time!
921898-0
« Last Edit: February 04, 2020, 02:04:47 pm by Spitfire1.2 »
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Offline EEEnthusiast

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Re: NPN & PNP LTspice
« Reply #1 on: February 04, 2020, 02:06:30 pm »
Can  you reverse the C & E of Q2 and try again?
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Offline rstofer

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Re: NPN & PNP LTspice
« Reply #2 on: February 04, 2020, 03:09:17 pm »
What's R5 suppose to represent?
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Offline StillTrying

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Re: NPN & PNP LTspice
« Reply #3 on: February 04, 2020, 03:34:14 pm »
And what does R3 do, it just looks like a jumble of components to me. :)
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.  That took much longer than I thought it would.
 

Offline Spitfire1.2Topic starter

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Re: NPN & PNP LTspice
« Reply #4 on: February 04, 2020, 05:12:31 pm »
R5 is the Led resistor, sorry but I accidentaly moved it. R3 is simulating a load on the NPN. The PNP was reversed  :palm:, i took it for granted that the collector was on the botton. Thanks for the help!
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Offline Zero999

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Re: NPN & PNP LTspice
« Reply #5 on: February 05, 2020, 12:24:58 pm »
What is the circuit supposed to do?

Try varying the supply voltage and see what happens to the LED current.
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