Fuzz simulation - Ge Transistor

[seweryn]

Hi. I'm struggling with Fuzz simulation, the problem is AC128 transistor.

Ge PNP model works in LTspiceIV,

this model imported to Multisim 13 won't work,

component created in Multisim 13 -based on BJT_PNP->Bjt,PNP,Ge doesn't work either...

is it bug is Multisim software ??, any working germanium component/model for Multisim exists ??

B.R.Seweryn.

[Chen_T]

Hi B.R.Seweryn,

The LT-Spice and Multisim Spice Models are different ones, that is why it's won't work when you import this Model to Multisim 13.

Right now the semiconductors today are almost silicon based. However, you can create your own Germanium components by modifying the Spice Model for your fuzz simulation. 

For a typical Ge transistor, the ON voltage ranges from 0.2-0.3V. Its forward resistance usually around hundreds Ohms.

Here is a link might be helpful to create your own model in Multisim

https://decibel.ni.com/content/groups/circuit/blog/2011/05/24/create-a-component-part-2-using-the-mo...

Also, in the RF Database, all the tunnel diodes are fabricated on Germanium substrates. In these links you can find the datasheets from their manufacturers:

http://www.aeroflex.com/ams/metelics/micro-metelics-prods-TD-MBD.cfm

http://store.americanmicrosemiconductor.com/1n3712.html

 Hope it helps.

Regards,

[seweryn]

as I mentioned "..component created in Multisim 13 -based on BJT_PNP->Bjt,PNP,Ge doesn't work either..."

i did create component in MS13 based on Natasha Baker tutorial....

But the component won't work as expected!!, completely doesn't act as germanium small signal transistor.

Anyway, I did follow your suggestions, and is even worst,

using Model Maker -> Bjt, won't accept model created by MM, pressing next cause error.. (see attach.)

Can you help?, is just few parameters and very quick job for MS experienced user..
-this way I can be sure it's worth spending time -because it will work..

Until now it looks to me like MS error.

[Chen_T]

Hi there,

I followed your steps and used Model Maker, it works fine. There is no MS error pop out. 

Test this attached file to see if it works.

Regards,

[seweryn]

thank you. ...but how is it possible ??

can you post screen dumps and mark entered/changed values please ??

I can't believe it !!

BTW. I have noticed

"* "On" Vbe1         = 5.600e-001 V at Ic = 1.000e-001 mA"

and it acts like Si...

[Chen_T]

Hi there,

The parameters are based on the datasheet I found.

I am using Multisim 13.01. In the Model Maker dialog, I modified the parameters as follows.

Try this model AC128_version2 that I made to see if it works. Also, you can just change the values from this file.

Hope it helps. 

Regards,

[seweryn]

gives:

------ Checking SPICE netlist for test3 - 21 lipca 2014, 13:39:51 ------ ======= SPICE Netlist check completed, 0 error(s), 0 warning(s) ======= Model 'ac128_version2__ac128_version2__1': Parameter 'VJC' must be greater than zero doAnalyses: Incorrect use of model parameters Simulation canceled

++

..which are same fields I used to touch plus:

&& Vbe~2V, band-witch~1MHz, and i still won't work as Germanium

[Chen_T]

Hi there,

Although I do not play guitar, there is a forum called "diyAudio", maybe they have some Germanium Transistor Spice Models for this particular type of fuzz simulation. 

http://www.diyaudio.com/forums/solid-state/117257-ac128-pnp-germanium-transistor-spice-mode-rare.htm...

Good luck to your fuzz tones design.

Regards,

[seweryn]

yep, have seen that before, and that model works (and nobody knows how reliable it is),

afterwards you can't edit parameters and so...

but why doesn't work as usual way providing the data (Component Wizard) ??

what is wrong with it ??

The question remains...

"is it bug is Multisim software ??, any working germanium component/model for Multisim exists ??"

[Chen_T]

Hi there,

I've checked the database, so far there is no pure Ge transistors left.

Regards,