I want to simulate the dependence of BetaDC on the current collector bias current for a 2N3904, by using LTSpice.
So I used a fixed VCE (5V) using a constant voltage source and a DC current source Ib applied at the base.
Then I performed a DC analysis simulation in which the sweep variable is the current source Ib and plotted the quantity:
Ic(q1) / Ib(q1)
versus Ic
The results are wrong:
[136 kB]
Where I am mistaking? Thanks in advance.
CURVEBETAdc.ASC
Version 4 SHEET 1 2472 1528 WIRE 2128 1152 1984 1152 WIRE 1984 1200 1984 1152 WIRE 2128 1216 2128 1152 WIRE 1920 1248 1840 1248 WIRE 1840 1264 1840 1248 WIRE 1840 1360 1840 1344 WIRE 1984 1360 1984 1296 WIRE 2128 1360 2128 1296 FLAG 2128 1360 0 FLAG 1984 1360 0 FLAG 1840 1360 0 SYMBOL npn 1920 1200 R0 SYMATTR InstName Q1 SYMATTR Value 2N3904 SYMBOL voltage 2128 1200 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName VC SYMATTR Value 5 SYMBOL current 1840 1344 M180 WINDOW 0 23 79 Left 0 WINDOW 3 24 0 Left 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName IB SYMATTR Value 10µ TEXT 1806 1384 Left 0 !.dc IB 0 50u .05u