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Old 21st December 2006, 02:31 AM   #1
sss is offline sss  Israel
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Default new thermal trak transistors

from on semi...
http://www.onsemi.com/PowerSolutions...tem.do?id=1218
did somebody tried those allready?
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Old 21st December 2006, 03:39 PM   #2
audioPT is offline audioPT  Portugal
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yes,

OnSemi sent me samples of some of the newest devices and I only can say they sound better than Sanken SAP's...
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Old 21st December 2006, 06:31 PM   #3
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They sound good, and with the thermal diodes in the bias circuit, the amps stays very stable
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Old 21st December 2006, 07:06 PM   #4
mikeks is offline mikeks  United Kingdom
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Unhappy A Missed Opportunity.

What OnSemi ought to have done is include another transistor on the same substrate as the power device for biasing with a Vbe-multiplier.

Then the things would probably have sold like hot cakes.
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Old 21st December 2006, 07:29 PM   #5
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Quote:
Originally posted by audioPT
yes,

OnSemi sent me samples of some of the newest devices and I only can say they sound better than Sanken SAP's...
Which schematic did you use?
I ask because at a quick glance the SAPs have several diodes integrated while ONSemi's seem to have just a diode and thus (like in their application note) there seems to be the need of multiple devices to achieve a correct polarization of the output stage...

Cheers

Andrea
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Old 21st December 2006, 08:11 PM   #6
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Quote:
Originally posted by Andypairo


Which schematic did you use?
I ask because at a quick glance the SAPs have several diodes integrated while ONSemi's seem to have just a diode and thus (like in their application note) there seems to be the need of multiple devices to achieve a correct polarization of the output stage...


It's not strictly necessary. Diodes embedded in onsemi devices may be used as a sensor for a second circuit (just the usual VBE mult a bit rearranged) that really "track" the idle current against temperature.
However is a very niceful idea! With appropriate circuit this device may really help to keep at minimun crossover distortion in Class AB amplifier especially when the output devices are the only that commute on zero crossing and when driver and predriver stages are keep in a continous conduction state (really a kind of non linear class A).

Normally, if crossover is restricted to the effective power devices, crossover distortion - in well trimmed amplifier of couse! - became hardly detectable without measurement. If bias control tracking with temperature is thermally improved as Onsemi device promises, crossover may became hardly detectable *even* with instrumental measurement. May be a real improvement toward theoretical minima of crossover distortion (for bipolar devices at least) without excessive entanglement of output stage topologies.

Ciao
Piercarlo
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Old 21st December 2006, 08:23 PM   #7
forr is offline forr  France
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Mikeks
---What OnSemi ought to have done is include another transistor on the same substrate as the power device for biasing with a Vbe-multiplier.---

A dream for amplifier engineers since more than thirty years. Manufacturers seem to have the worst difficulities to understand it. At last they are on the right way, but still far from the real demand.
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Old 21st December 2006, 08:23 PM   #8
Nordic is offline Nordic  South Africa
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http://www.tubecad.com/2006/10/blog0084.htm
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Old 21st December 2006, 08:55 PM   #9
audioPT is offline audioPT  Portugal
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Quote:
Originally posted by Andypairo


Which schematic did you use?
I ask because at a quick glance the SAPs have several diodes integrated while ONSemi's seem to have just a diode [...]

Quote:
Originally posted by Piercarlo


It's not strictly necessary. Diodes embedded in onsemi devices may be used as a sensor for a second circuit (just the usual VBE mult a bit rearranged) that really "track" the idle current against temperature.
[...]
I have done just like Piercarlo said! A fancy VBE multiplier

One 10uF Cap!

I've used OnSemi schematic, only from VAS to output. I've used a differential pair with current mirrors at the input.
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Old 21st December 2006, 09:09 PM   #10
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I don't believe additional diodes would help them to compete against Toshiba.
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