Temperature compensation in LTSpice?

[Bill Bowden]

Is it possible to simulate circuit performance using LTSpice under
different temperature conditions? Say you have a single NPN transistor
with grounded emitter and a collector load and a resistor from base to
collector so the collector voltage is about half the supply voltage. I
understand the result would depend on the HFE of the transistor,
temperature, and maybe not very stable. Just wondering if LTSpice can
provide any interesting information for some particular transistor. DC
voltage change verses temperature.

-Bill

 

[George Herold]

Here's a simple temperature sweep example:

https://dl.dropbox.com/u/53724080/Circuits/TC_diode_sweep.asc

Hey dropbox is pretty cool! (I need to investigate)

George H.

 

[Bill Bowden]

Here's a simple temperature sweep example:

https://dl.dropbox.com/u/53724080/Circuits/TC_diode_sweep.asc

Yes, that works fine to plot the e/b and b/c voltage temp conditions.
I tried adding a spice directive of (.step temp 0 50 5) to my
transistor stage and I get 10 lines displayed (5 to 6 volts) which I
presume correspond to the 10 temperature steps. But the display
doesn't indicate what voltage occurs at what temperature. How to fix
that?

-Bill

Version 4
SHEET 1 880 680
WIRE 144 16 16 16
WIRE -128 144 -192 144
WIRE 16 144 16 96
WIRE 16 144 -64 144
WIRE 16 208 16 144
WIRE -192 256 -192 144
WIRE -160 256 -192 256
WIRE -48 256 -80 256
WIRE 16 320 16 304
FLAG 144 96 0
FLAG 16 320 0
SYMBOL voltage 144 0 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 12
SYMBOL npn -48 208 R0
SYMATTR InstName Q2
SYMATTR Value 2N3904
SYMBOL res 0 0 R0
SYMATTR InstName R3
SYMATTR Value 22k
SYMBOL res -64 240 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R4
SYMATTR Value 5000k
SYMBOL diode -64 128 R90
WINDOW 0 0 32 VBottom 0
WINDOW 3 36 -4 VTop 0
SYMATTR InstName D2
SYMATTR Value 1N4148
TEXT -40 392 Left 0 !.step temp 0 50 5
TEXT -200 392 Left 0 !.tran .1s

 

[Fred Abse]

But the display doesn't indicate
what voltage occurs at what temperature. How to fix that?

Right click on the plot screen. Click on "Select Steps"