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Question on NPN Logic Inverter From Textbook
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eev_carl:
Hi,

I created an LT Spice of this logic inverter from a textbook (Jaeger and Blalock, 3rd edition "Microelectronic Circuit Design").  I'm getting a Vce that's 10x less than what's printed in the book. I was wondering if someone could help troubleshoot my model.  In the sim, I get a Vce of 18mV and the book (see attachments) has it listed at 180mV.  Maybe I'm not measuring the right thing?

Thanks,
Carl
eev_carl:
It's cut off in the photo, but the figure from the book below the text is 5.32(a).
Wimberleytech:
Pick a 2n3904 model for you simulation and see what you get.

You are being kinda hard on that poor transistor forcing 1 volt Vbe.

Add some base resistance.
eev_carl:
2n3904

V(vce):    0.00810523    voltage
rstofer:
VceSat is usually on the order of 0.2V (MAX at Ic=10 mA).  Your simulation shows about 1/10th that amount and it is probably an issue with the model.

Look at the 2d page of the 2N3904 dataseet and you will see that VceSat is also a function of collector current.  The lower the current, the lower the saturation voltage.

https://www.onsemi.com/pub/Collateral/2N3903-D.PDF

Page 6 shows VceSat of 0.1V for currents less than about 10 mA. 

Try it with a real circuit!
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