LTSpice triode model

[Andrew Holme]

I found these triode models:

http://www.duncanamps.com/spice/valves/dmtriodep.inc

The LTSpice .asc file below shows anode current when Vgc < -80V. Do valves
do this, or is it a bug in the model? What's the fix?

Version 4
SHEET 1 2020 680
WIRE 928 176 832 176
WIRE 928 192 928 176
WIRE 832 288 832 176
WIRE 928 288 928 272
WIRE 928 336 880 336
WIRE 928 368 928 336
WIRE 864 464 864 384
WIRE 928 464 928 448
FLAG 928 288 0
FLAG 928 464 0
FLAG 864 464 0
SYMBOL voltage 928 176 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName Va
SYMATTR Value 150
SYMBOL Misc\\triode 832 336 M0
SYMATTR InstName U1
SYMATTR Value NH12AU7
SYMATTR SpiceModel NH12AU7
SYMBOL voltage 928 352 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName Vgc
SYMATTR Value ""
TEXT 1040 288 Left 0 !.include dmtriodep.inc
TEXT 1040 368 Left 0 !.dc Vgc -150 0

 

[Fred]

I found these triode models:

http://www.duncanamps.com/spice/valves/dmtriodep.inc

The LTSpice .asc file below shows anode current when Vgc < -80V. Do valves
do this, or is it a bug in the model? What's the fix?

Version 4
SHEET 1 2020 680
WIRE 928 176 832 176
WIRE 928 192 928 176
WIRE 832 288 832 176
WIRE 928 288 928 272
WIRE 928 336 880 336
WIRE 928 368 928 336
WIRE 864 464 864 384
WIRE 928 464 928 448
FLAG 928 288 0
FLAG 928 464 0
FLAG 864 464 0
SYMBOL voltage 928 176 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName Va
SYMATTR Value 150
SYMBOL Misc\\triode 832 336 M0
SYMATTR InstName U1
SYMATTR Value NH12AU7
SYMATTR SpiceModel NH12AU7
SYMBOL voltage 928 352 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName Vgc
SYMATTR Value ""
TEXT 1040 288 Left 0 !.include dmtriodep.inc
TEXT 1040 368 Left 0 !.dc Vgc -150 0

Basically there are two kinds of triode models, the Leach and the
Koren. I favor the Koren models. I have found them to be reasonably
accurate if you stay within normal operating parameters. Get too far
away from that and the models get quirky.

Best regards,

Fred

 

[Tim Williams]

I found these triode models:

http://www.duncanamps.com/spice/valves/dmtriodep.inc

The LTSpice .asc file below shows anode current when Vgc < -80V. Do
valves do this, or is it a bug in the model? What's the fix?

I don't know (or care ;-) ) much about SPICE, but I know plenty about 12AU7.
If plate voltage is over 1kV or so, I might expect to see some current
at -80Vg. At any plate voltage, there will be some leakage, which should be
much less than a miliampere, especially at -80Vg.

Tim

 

[Andrew Holme]

I don't know (or care ;-) ) much about SPICE, but I know plenty about
12AU7. If plate voltage is over 1kV or so, I might expect to see some
current at -80Vg. At any plate voltage, there will be some leakage, which
should be much less than a miliampere, especially at -80Vg.

The above model is very wrong at Vg < -80V.

I've just found a better one on the same website:

http://www.duncanamps.com/spicevalvest.html#12AU7A

 

[Andrew Holme]

The above model is very wrong at Vg < -80V.

I've just found a better one on the same website:

http://www.duncanamps.com/spicevalvest.html#12AU7A

Better in one way, worse in another

This manages to suck 22.8mA through a 68K anode load resistor from a 150V
supply, giving an anode voltage of -1.4KV.

 

[Andrew Holme]

Better in one way, worse in another

This manages to suck 22.8mA through a 68K anode load resistor from a 150V
supply, giving an anode voltage of -1.4KV.

I'm now trying the Norman Koren models, which seem to take anode voltage
into account and do sensible things at both extremes of grid voltage.