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Old 10th January 2009, 02:51 PM   #671
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Quote:
Originally posted by ostripper
..he would call you "a boring person"

Sounds like my ex-wife!

You are creating quite a stable of designs here. No shortage of choices for sure.
I've been busy for a few days and I'll need to do some catching up.
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Old 10th January 2009, 06:04 PM   #672
jaycee is offline jaycee  United Kingdom
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Quote:
Originally posted by ostripper
Yes ,JC, they look good ,but WTF no models. Fairchild
sucks in this way, they have good models for some but are
very incomplete in their listing. They want us to buy their
$#$T ,but don't even supply us with adequate design
resources...ARggg
They do have models... they will only email them to you instead of download, but they have them.

AS they stand, they're a subcircuit which models both the transistor and the thermal parameters, but it is trivial to change it to a straight transistor model. Here you go:

.MODEL FJP5200 npn (
+ IS = 1.24896E-10 BF = 220.2 NF = 1
+ BR = 1.025 NR = 1.0 ISE = 2.04807E-8
+ NE = 2.0 ISC = 2.01764E-9 NC = 1.5
+ VAF = 188.7 VAR = 100 IKF = 5.2182
+ IKR = 1.39087 RB = 22.1 RBM = 0.00011
+ IRB = 1.51189E-6 RE = 0.0032 RC = 0.0183
+ CJE = 1.132025E-10 VJE = 0.711 MJE = 0.304
+ FC = 0.5 CJC = 6.88229E-10 VJC = 0.84
+ MJC = 0.25 TF = 5.1703E-9 TR = 3.342E-7
+ XTB = 1.72 EG = 0.78 XTI = 3)

.MODEL FJP1943 pnp (
+ IS = 6.04896E-11 BF = 200.2 NF = 1
+ BR = 8.805 NR = 1.0 ISE = 8.24807E-9
+ NE = 2.0 ISC = 4.01764E-10 NC = 1.5
+ VAF = 18.7 VAR = 20 IKF = 2.2182
+ IKR = 0.19087 RB = 1.1 RBM = 0.000011
+ IRB = 1.51189E-9 RE = 0.00611 RC = 0.0103
+ CJE = 1.132025E-10 VJE = 0.711 MJE = 0.304
+ FC = 0.5 CJC = 6.88229E-10 VJC = 0.84
+ MJC = 0.25 TF = 5.3703E-9 TR = 3.342E-7
+ XTB = 2.28 EG = 0.81 XTI = 3)
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Old 10th January 2009, 06:14 PM   #673
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Thank you , JC . I know they email them to you, I have done it.
but they don't have them ,you do..but they don't..(see attachment) they also don't have models for their Ksa 2682
and many other of their products.

I looked on this page:
http://www.fairchildsemi.com/models/...ransistor.html
No dice! only 2 FJP-XXX's there . Is there another page??
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Old 10th January 2009, 06:22 PM   #674
jaycee is offline jaycee  United Kingdom
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Go to the actual product page for the device in question. If they have a model for the device, there will be a link "Models" in the Contents section of the page.

My guess is they maintain the models page by hand, and they havent updated it - a stupid thing to do, but well there you go
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Old 10th January 2009, 06:28 PM   #675
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Your right,found them..(how stupid of them/me) I guess they just want to sell,sell...
OS
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Old 12th January 2009, 06:44 AM   #676
jaycee is offline jaycee  United Kingdom
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Got a few ideas after looking at your FA3:

Q8/Q11 dont have to dissipate much power - you could use KSA992/KSC1845 there instead. Then make Q9/Q10 the KSA1220/KSC2690's instead.

How about changing the mirror Q6/Q7 into a Wilson mirror ? Normally Q6 dissipates about 2mW and Q7 around 200mW which could unbalance it.. in a Wilson mirror the power would be dissipated in the 3rd transistor but this wouldn't affect the mirror's balance.

Personally I'm still diddling with my Cyrus input stage affair. The KSC1845/KSA992 have actually improved things a lot. My guess is speed is important in the input stage, the Cyrus One used very fast small signal devices (200MHz fT) here and in the VAS.

Who knows what i'll end up with though!
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Old 12th January 2009, 07:46 AM   #677
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Quote:
Who knows what i'll end up with though
I beginning to go crazy with all the good ideas around here..

just ported the current amp of the krill to the front end of the FA3
and came up with ..WOW..
Here is the circuit.. download in the frugalamp folder FA3K.asc
to play..
OS
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Old 12th January 2009, 08:07 AM   #678
jaycee is offline jaycee  United Kingdom
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Hehe yeah I saw that and wonder if you'd seen the Marantz 300DC schematic like I have

I'm wondering if the diamond buffer would be better applied as a predriver stage - see this for example:

http://home.no.net/andiha/articles/audio/claclassa.htm

He calls the amplifier "Classical Class A" but really it's Class AB heavily biased. Incidentally the designer of that amp is using the same 2SA872/2SC1775 as the Cyrus 1 does.
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Old 12th January 2009, 11:49 AM   #679
AndrewT is offline AndrewT  Scotland
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Quote:
Originally posted by jaycee


I'm wondering if the diamond buffer would be better applied as a predriver stage - see this for example:

http://home.no.net/andiha/articles/audio/claclassa.htm

He calls the amplifier "Classical Class A" but really it's Class AB heavily biased. Incidentally the designer of that amp is using the same 2SA872/2SC1775 as the Cyrus 1 does.
this is a real ClassA amplifier.
25W into 8r0 if biased to >=1.25A
and 30W into 6r0 if biased to >=1.6A

He does explain that it goes into ClassAB if the ClassA output current is exceeded and quotes 2r0 use to support his reliability claims of the design.
__________________
regards Andrew T.
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Old 13th January 2009, 01:33 PM   #680
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Quote:
By JC - I'm wondering if the diamond buffer would be better applied as a predriver stage - see this for example
Yes,yes ,yes...a wonderful predriver stage..
After reading about the diamond buffer,dissecting the "krill"
i have been won over to this technique. Steve dunlap explained
it to me very good but after playing with it, I wanted to
go solo (more like the marantz dc300).
Click the image to open in full size.

This arrangement differs from the krill in 3 ways , 1. use of
a standard Vbe and 2 diodes bootstrapped (like the marantz)
2. Full global NFB instead of VAS only (eliminates CCS's
for the diamond (also like the marantz) 3. Use of the wonderful
input stage of the FA3.

This one has been fun to Simulate and performs better
than any I've done yet.. Very strange loopgain ,flat with
no "hump" at the end like a blameless or P3A type topology.

I first tweaked an isolated "krill" type current stage
to get rid of oscillations (fast newer devices) then
realized any VAS could be attached (used mine).
The only question that remains is feedback.. Does the
original Current stage without feedback or associated
influence from the dynamic speaker load make for a
better sound than a global NFB arrangement.

Even with steve's current sources improved with IC's(lm234z)
the global feedback version (above) does better
distortion wise. The marantz (more like mine is highly regarded
for it's sound..so I guess I'll have to build it to find out..
OS
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