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6th October 2007, 02:56 AM  #1 
diyAudio Member
Join Date: Feb 2007
Location: SoCal

6BX7 PSpice Model?
Hi, I am looking for PSPice model for 6BX7. Or I can modify one from 6SN7 if I can get those numbers. It is a headphone amp project. I am planning to use it as CF output.
Thanks. 
6th October 2007, 01:30 PM  #2 
diyAudio Member
Join Date: May 2005
Location: Stittsville, Ontario, Canada

Hello :
try this one * 6BX7  IDH mediummu hightransconductance twin Bp A K I=(m)*uramp(()*V(G,K)+V(A,K))**1.5 * From GE 6BX7GT datasheet  traced on 190104 by AF .subckt mk_6BX7 A G K Cgp G P 4.2p Ci G K 4.4p Co A K 1.1p * Modified Koren model (8 parameters): mean fit error 0.573819 mA Bp A K I=(0.1001852541m)*uramp(V(A,K)*ln(1.0+(0.1116255831)+exp((3.282351583)+(3.282351583)*((12 .22538987)+(24.13446294m)*V(G,K))*V(G,K)/sqrt((0.04128697397)**2+(V(A,K)(6.806029609))**2)))/(3.282351583))**(1.44441018) .ends mk_6BX7 I do not remember where I got this model, I think it was from a thread here about how Koren's 5 parameter model could be improved with 6, 7 or 8 parameters.
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Robert McLean 
7th October 2007, 05:55 PM  #3 
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Join Date: Feb 2007
Location: SoCal

Thanks Robet.
I copied the code into my Orcad Spice model and got this error ERROR  Line too long. Limit is 132 characters. Any ideas? 
8th October 2007, 02:17 PM  #4  
diyAudio Member
Join Date: May 2005
Location: Stittsville, Ontario, Canada

splitting up SPICE lines
Quote:
The method for splitting up SPICE lines is to use a "+" at the start of the next line. This marks it as the start of a continuation line. It can be a bit confusing ( to a human reader, not to spice) knowing if the + is a continuation sign, or a normal addition sign, so I put lots of spaces in to show it is a continuation So here is the same code with shorter lines : * 6BX7  IDH mediummu hightransconductance twin * Bp A K I=(m)* uramp(()*V(G,K)+V(A,K))**1.5 * From GE 6BX7GT datasheet  traced on 190104 by AF .subckt mk_6BX7 A G K Cgp G P 4.2p Ci G K 4.4p Co A K 1.1p * Modified Koren model (8 parameters): * mean fit error 0.573819 mA Bp A K I=(0.1001852541m)*uramp(V(A,K)*ln(1.0+( + 0.1116255831)+exp((3.282351583)+(3.282351583)* + ((12.22538987)+(24.13446294m)*V(G,K))*V(G,K)/sqrt + ((0.04128697397)**2+(V(A,K)(6.806029609))**2)))/ + (3.282351583))**(1.44441018) .ends mk_6BX7 that should work now. Interesting note : when I preview this message, the extra spaces I put in have disappeared. This wont affect how the model works.
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Robert McLean 

8th October 2007, 08:40 PM  #5 
diyAudio Member
Join Date: Apr 2005
Location: NJ

Here's another:
* Generic triode model: 6BX7 * Copyright 20032006 by Ayumi Nakabayashi, All rights reserved. * Version 3.01, Generated on Wed Mar 22 17:19:49 2006 .SUBCKT 6BX7 A G K BGG GG 0 V=V(G,K)+0.99999999 BEP EP 0 V=URAMP(V(A,K))+1e10 BEG EG 0 V=URAMP(V(G,K))+1e10 BM1 M1 0 V=(0.044756942*(URAMP(V(EP)1e10)+1e10))^0.87869992 BM2 M2 0 V=(0.63059657*(URAMP(V(GG)+V(EP)/8.253545)+1e10))^2.3786999 BP P 0 V=0.0032697035*(URAMP(V(GG)+V(EP)/13.088471)+1e10)^1.5 BIK IK 0 V=U(V(GG))*V(P)+(1U(V(GG)))*0.0020437592*V(M1)*V(M2) BIG IG 0 V=0.0016348517*V(EG)^1.5*(V(EG)/(V(EP)+V(EG))*1.2+0.4) BIAK A K I=URAMP(V(IK,IG)URAMP(V(IK,IG)(0.0020166439*V(EP)^1.5)))+1e10*V(A,K) BIGK G K I=V(IG) * CAPS CGA G A 4.2p CGK G K 4.8p CAK A K 1.2p .ENDS 
11th October 2007, 04:10 AM  #6 
diyAudio Member
Join Date: Feb 2007
Location: SoCal

This time I got a different error:
**** EXPANSION OF SUBCIRCUIT X_VL1 **** X_VL1.Cgp N731296 X_VL1.P 4.2p X_VL1.Ci N731296 N604658 4.4p X_VL1.Co N604270 N604658 1.1p X_VL1.Bp N604270 N604658 X_VL1.I X_VL1.0.1001852541m *uramp $ ERROR  Invalid parameter Is Orcad Spice different from what your guys use? 
11th October 2007, 05:53 AM  #7  
diyAudio Member

Quote:
These errors look like they're from spice or orcad itself. Them's some big node numbers ! (Ex. N731296) Are you starting from an example circuit ? If not, that might be easier. boB 

11th October 2007, 10:45 PM  #8 
diyAudio Member
Join Date: May 2005
Location: Stittsville, Ontario, Canada

Orcad PSpice
Orcad PSpice does not like the uramp function. So you need to rewrite the models slightly by replacing
uramp( blablabla ) with limit( blablabla, 0, 1e16 ) Here is my model rewritten in PSpice * 6BX7  IDH mediummu hightransconductance twin * Bp A K I=(m)* uramp(()*V(G,K)+V(A,K))**1.5 * From GE 6BX7GT datasheet  traced on 190104 by AF .subckt mk_6BX7 A G K Cgp G P 4.2p Ci G K 4.4p Co A K 1.1p * Modified Koren model (8 parameters): * mean fit error 0.573819 mA Bp A K I=(0.1001852541m)*limit(V(A,K)*ln(1.0+( + 0.1116255831)+exp((3.282351583)+(3.282351583)* + ((12.22538987)+(24.13446294m)*V(G,K))*V(G,K)/sqrt + ((0.04128697397)**2+(V(A,K)(6.806029609))**2)))/ + (3.282351583), 0, 1e16)**(1.44441018) .ends mk_6BX7
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Robert McLean 
14th October 2007, 09:50 PM  #9 
diyAudio Member
Join Date: Feb 2007
Location: SoCal

Still could not get the model to work. So I modified the a simple 6SN7 to fit the 6BX7 curve. Here is what I have:
* Connections: Plate *  Grid *   Cathode *    .SUBCKT 6BX7 A G K E1 2 0 VALUE={V(A,K)+10.43*V(G,K)} R1 2 0 1.0K Gp A K VALUE={200.89E6*(PWR(V(2),1.5)+PWRS(V(2),1.5))/2} Cgk G K 4.4P Cgp G A 4.2P Cpk A K 1.1P Rak A K 1G Rgi G X 2K D3 X K dx .model dx d(is=1n rs=1 cjo=0 tt=1n) .ENDS 6BX7 I powered up the headphone amp and took some measurements. The quiescent point is close enough (actual Ip <5% lower) in a CF application. I guess the more ciomplicated model will be closer? 
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