Variance of RF transconductance of audio bipolar transistors from different manufactu - diyAudio
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Old 29th August 2014, 06:06 AM   #1
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Default Variance of RF transconductance of audio bipolar transistors from different manufactu

Does anyone happen to have H-parameter charts or a datasheet with them for any of the BC5xx transistors? Or any other useful transistors for that matter?
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Old 29th August 2014, 06:56 AM   #2
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The reason I ask about the H-params is that based on my amplifier prototype the RF transconductance of the BC550C (Fairchild) is 2-3x worse than Cordell's SPICE models.
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Old 29th August 2014, 07:47 AM   #3
Elvee is offline Elvee  Belgium
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Quote:
Originally Posted by keantoken View Post
Does anyone happen to have H-parameter charts or a datasheet with them for any of the BC5xx transistors? Or any other useful transistors for that matter?
Here it is:
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File Type: pdf img-829084231-0001.pdf (43.9 KB, 41 views)
File Type: pdf img-829084434-0001.pdf (332.8 KB, 26 views)
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Old 29th August 2014, 08:04 AM   #4
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Quote:
Originally Posted by keantoken View Post
Does anyone happen to have H-parameter charts or a datasheet with them for any of the BC5xx transistors? Or any other useful transistors for that matter?
I have some, give an address I can send it all to.
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Old 29th August 2014, 10:28 AM   #5
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Quote:
Originally Posted by Elvee View Post
Here it is:
Thanks, unfortunately it's not what I wanted. There are some datasheets that give the H-param vs Frequency charts. These allow you to very accurately model the RF behavior. For instance:

https://www.engineering.uiowa.edu/si...1/DS013193.pdf

Here are some models for the MPSH10/MPSH81 (unfortunately obsoleted) that I quickly modified some time ago to improve the accuracy of shunt regulator simulations I was doing. I didn't change anything except the RF parameters:


.model MPSH81 pnp IS=1.364229E-15 BF=109 NF=1 ISE=1.59087E-16 NE=2 VAF=100
+ ISC=5.8e-9 BR=0.48 IKR=0.85 IKF=0.150527 RB=46.6 RBM=0.159 IRB=1.51356E-6
+ RE=0.23 RC=1.0 CJE=2.63E-12 VJE=0.80 MJE=0.335 FC=0.5 CJC=2.77E-12 VJC=0.757
+ MJC=0.158 XTB=1.59999 EG=0.86 XTI=3 TF=97.83e-12 ITF=69.29 VTF=10
+ XTF=599e-6
.MODEL MPSH10 NPN(IS=5.6E-16 ISE=6.367E-15 ISC=1E-15 XTI=3
+ BF=133 BR=8 IKF=2.5E-2 IKR=1E-2 XTB=1.5
+ VAF=40 VAR=6 VJE=1.195 VJC=0.5617
+ RE=0.65 RC=1.8 RB=150 RBM=0.5 IRB=5E-4
+ CJE=1.012E-12 CJC=1.197E-12 XCJC=0.75 FC=0.5
+ NF=1 NR=0.99 NE=1.75 NC=1.167 MJE=0.4496 MJC=0.2588
+ TF=6E-11 TR=40.5E-9 ITF=0.27 VTF=10 XTF=30
+ EG=1.11 KF=1E-9 AF=1
+ VCEO=25 ICRATING=50m MFG=ZETEX)
.model MPSH81_k AKO:MPSH81 Fc=0.9 Itf=1.15 Vje=.75 Vtf=10 Xtf=10 Tf=87p
.model MPSH10_k AKO:MPSH10 (Fc=0.9 Itf=2 Vje=.75 Vtf=10 Xtf=10 Tf=90p Rb=47)

The first two are the standard models and the last two with the _k suffix are my improvements. Separating them will break them because the latter references the former.

Transconductance vs Frequency is a characteristic that isn't strongly related to Ft, but is very important in the MHz region and can have an effect on feedback loops. Ft vs Ic charts aren't sufficient to model this.
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Last edited by keantoken; 29th August 2014 at 10:30 AM.
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Old 29th August 2014, 10:58 AM   #6
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I am afraid this data is generally not available for LF transistors. The MPSH series are RF transistors
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Old 30th August 2014, 08:31 PM   #7
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Quote:
Originally Posted by keantoken View Post
The reason I ask about the H-params is that based on my amplifier prototype the RF transconductance of the BC550C (Fairchild) is 2-3x worse than Cordell's SPICE models.
I made some measurements on a number of samples from various manufacturers.

These are not "metrological" grade measurements: they are scalar, uncalibrated, and made on something that is more a toy that anything, but it gives a taste of what it looks like, and there are significant differences between founders.
I may repeat those measurement on a properly calibrated VNA, but it will take some time.
The first pic shows the equivalent circuit of the test jig; for not too high frequencies, it should return the value of gm without too many parasitic effects.
Vce is 5V and Ic 5mA (the bias is adjusted for Ic).

Second pic is the parade of DUT's
From left to right: 2N3904 Moto, BF240 Phil (gold standard), BC548C Moto, BC413B Sesco (=Silec, Thomson, ST, ), BC548C Philips, BC548B Telefunken, BC548C Multicomp, BC238C Fairchild.

There are indeed significant differences, between devices and also between the reality and simulation.

PS:

the measurement range is ~0 to 50MHz

Moderators: if you could split the posts pertaining to this particular subject from this thread and create a new discussion in solid state, it would be a good thing
Attached Images
File Type: jpg BC548TestJig.jpg (302.5 KB, 292 views)
File Type: jpg BC548PARADE.jpg (93.5 KB, 287 views)
File Type: jpg 2N3904MOTO.jpg (185.1 KB, 279 views)
File Type: jpg BF240PH.jpg (202.7 KB, 276 views)
File Type: jpg BC548Cmoto.jpg (192.8 KB, 270 views)
File Type: jpg BC413Bsesco.jpg (180.5 KB, 75 views)
File Type: jpg BC548CPHIL.jpg (192.4 KB, 70 views)
File Type: jpg BC548BTFK.jpg (197.3 KB, 64 views)
File Type: jpg BC238CFAIR.jpg (191.8 KB, 56 views)
File Type: jpg BC548CMULTI.jpg (206.7 KB, 68 views)
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Last edited by Elvee; 30th August 2014 at 08:38 PM.
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Old 31st August 2014, 11:32 AM   #8
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Quote:
Originally Posted by Elvee View Post
I made some measurements on a number of samples from various manufacturers.
Thanks a lot. I don't know how to read spectrum analyzer displays, but the BC5xx definitely have the transconductance droop that I expected. I would think if this was caused by Rb, the simulation would show it accurately.

Interesting that the Motorola BC5xx are faster. I believe OnSemi obtained Motorola, and IIRC the OnSemi BC5xx datasheets are basically copies of the Motorola datasheets, with different capacitance specs than Fairchild and NXP/Phillips. I have some OnSemi BC5xx I can try out.

I think the test would be more accurate if you could put the transistor base at ground, collector decoupled, inject the signal directly into the emitter, and read the emitter voltage. This way we wouldn't have Cob and Early effect in the way.
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Old 31st August 2014, 11:48 AM   #9
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Cordell's model is accurate here. So I'm starting to think the discrepancy is elsewhere in my circuit.
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File Type: png Transadmittance-BC550C-simulation.png (74.0 KB, 189 views)
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Old 6th June 2015, 04:29 PM   #10
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Posts relocated and new thread created per OP request.
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