AC128 PNP Germanium Transistor Spice Model (Rare!)

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pweaudiotech

Member
2008-02-11 6:30 pm
AC128 PNP Germanium Transistor Spice Model

I found it!...i found it!...i have searched the internet for years looking for this..the one...the only! Ac128 pnp germanium transistor spice model!

Note: this is a typical .cir type file spice model:

*AC128 PNP Germanium Transistor Spice Model
*
.MODEL AC128_X PNP IS=1.41f ISC=0 ISE=0 IKF=80m IKR=0 ITF=0.4
+NC=2 NE=1.5 BF=70 BR=4.977 RB=10 RC=2.5 CJC=9.728p CJE=8.063p
+TR=33.42n TF=179.3p FC=0.5 EG=1.11 VJC=0.2 VJE=0.2 VTF=4
+MJC=0.5776 MJE=0.3677 XTB=1.5 XTF=6 XTI=3


Note for a "matched" npn germanium transistor spice model:

*AC127 NPN Germanium Transistor Spice Model
*
.MODEL AC127_X NPN IS=1.41f ISC=0 ISE=0 IKF=80m IKR=0 ITF=0.4
+NC=2 NE=1.5 BF=70 BR=4.977 RB=10 RC=2.5 CJC=9.728p CJE=8.063p
+TR=33.42n TF=179.3p FC=0.5 EG=1.11 VJC=0.2 VJE=0.2 VTF=4
+MJC=0.5776 MJE=0.3677 XTB=1.5 XTF=6 XTI=3
 
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orbanp

Member
2007-07-25 2:36 pm
These models are quite bad!
Vbe is around 0.7V, a common emitter amplifier with about 50dB gain has an upper frequency of about 7MHz! That is nothing like using those old germanium transistors with an Ft of 1.5MHz!
If you plug in 2N3906, a jelly bean type Si PNP transistor, you get similar results.
Looks like someone just renamed a simple Si transistor model!

Peter
 
Yes, I saw this same complaint in regard to a book review.
That improperly hacked silicon models were abused.

http://www.amazon.com/Digital-Guitar-Modeling-William-Overton/dp/3836461943

I do not yet know if its true or not. But I have a forklift of
opposing Aleph offset voltage followers to sim and build.
(Giant basakwerdized diamond buffer)... And was wanting
to use complimentary germanium VBE's for the smallest
reasonable offset tracking references.

Tighter the offset voltage gap (similar function to VAS in
my circuit), the better output damping in my application.
But I couldn't make either of these germanium emitters
simulate as expected...

My actual transistors are 2N169A, which is an NPN I think?
I have to go home and look what the PNP number was....
Suspect it was a 2N383, but thats goin by foggy memory.

I am using LTSpice IV.
 

wg_ski

Member
2007-10-10 5:21 pm
kenpeter said:
So, which spice parameter of the above is the most broken?


Probably all of them. To do it right, you'd have to generate Gummel plots and CV characteristics for those Ge devices, and hope the model has enough flexibility to fit the data. Spice models weren't designed with germanium in mind. I work mostly with microwave FET models, and models originally designed for one material and technology don't always fit well with newer devices. Sometimes you have to go in and alter the code and equations to even get close.
 

GK

Disabled Account
2006-01-08 4:35 am
F-ing BS microsoft

That looks like a fantastic application. I just started creating a spice model for the MJE15028.

I got to the point in the instructions - "Invoke solver".

Where the Fk is that then!

Argghh!
 

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GK

Disabled Account
2006-01-08 4:35 am
PH104 said:
Glen --

It's one of those irritating MS add-in things. Go to Tools, then Add-Ins. You might need to have the install disc handy, can't remember.

Anything good cooking?

Phil


Ahh!

Thanks! I was almost ready to head butt the computer out the window.

No curried baked beans on the stove at the moment.

Cheers,
Glen
 

GK

Disabled Account
2006-01-08 4:35 am
Yahoo!

Here is my first attempt at making a SPICE model.

It is a MJE15028.

Using this model I'm no getting realistic emitter follower bandwidth results in LTspice (the ON Semi models just return garbage).

I'd appreciate it if any of the SPICE experts out there could give it a look over.


.model MJE15028 NPN (VAF=100 IS=9.3E-08
+NF=1.66465 BF=400 NE=2.99976
+ISE=1.97E-07 IKF=0.86181 MJE=0.19
+CJE=1070p VJC=1 MJC=0.416871
+CJC=287.1405p VJC=0.4 TF=5.31E-09)
 

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orbanp

Member
2007-07-25 2:36 pm
Re: Yahoo!

I have not looked at the model, but in your test circuit the transistor is not properly biased!
I would rather use a common emitter circuit, with a bypassed emitter resistor, biased for a collector current of your interest, in that case the upper frequency is defined by the transistor capacitances!

Peter


G.Kleinschmidt said:
Here is my first attempt at making a SPICE model.

It is a MJE15028.

Using this model I'm no getting realistic emitter follower bandwidth results in LTspice (the ON Semi models just return garbage).

I'd appreciate it if any of the SPICE experts out there could give it a look over.


.model MJE15028 NPN (VAF=100 IS=9.3E-08
+NF=1.66465 BF=400 NE=2.99976
+ISE=1.97E-07 IKF=0.86181 MJE=0.19
+CJE=1070p VJC=1 MJC=0.416871
+CJC=287.1405p VJC=0.4 TF=5.31E-09)
 

GK

Disabled Account
2006-01-08 4:35 am
Re: Re: Yahoo!

orbanp said:
I have not looked at the model, but in your test circuit the transistor is not properly biased!


Hi.

Look closer!

The AC source has a DC value of 5V, so the transistor is biased at ~1A.

BTW, there was a typo in my previous post - I meant to say that I was getting realistic results.
 

Elvee

Member
2006-09-08 2:04 pm
For those still interested in germanium models, I stumbled on some of them in an example from the educational circuits of LTspice.
They are in the simulated P2 opamp (Philbrick).
For example, here is the 2N344:

.model 2N344 PNP(Is=1e-10 bf=11 Vaf=15 Cje=5p Cjc=2.5p Tf=3n
+ Eg=.67 Rb=100 Re=10)

It is not perfect, but it is a good starting place that might be tweaked to accomodate other types.
Anyway, it is not grossly incorrect like the AC128 mentionned earlier.
 
I found the SPICE Model in a thesis on the J.H. Fuzz Box and all I wanted was something with a workable BF. The Fuzz Box design I have with SPICE has high gain transistors and I replaced the Feedback Loop Resistor with a Potentiometer to get much higher gain so I could use low hfe xistors. I downloaded the bjt.xls and will see what I can do with it...just have to find parameters for the Ge's...should take about...12 Billion Light Years on the Internet.
 
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