NJL4302/4281 Discontinued.

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I just realized that the NJL4281 & NJL4302 (ThermalTrak) are discontinued. The 3281 and 1302 are the stated "replacements" options. The 4xxx parts have better thermal conductance for more power, better Vce AND faster. So I just ordered 11.5 kilowatts of transistors before they become unobtainable. That should do me (it's only 50 after all).
So "heads up" to ThermalTrak users because there is not too much stock if ON Semi data is accurate.

David
 
I'd guess the higher cost has suppressed sales to below economic production level.

Shame, since the 180W device has a poorer SOA at the higher voltages. The 230W device is really good when PSU is supplying >=+-60Vdc and still performs adequately @ around +-80Vdc
 
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For discrete components like this, it's quite unusual for them to be EOL'd after such a short lifespan (other than low voltage mosfets in the computing market). Might be these are being discontinued because the assembly center is being moved and sales do not warrant the costs of transfer and requalification.
 
High manufacturing cost an low demand for theses devices.

Indeed , they are not that practical since they have no real equivalence ,
the Sanken s ones being different i think.

The lucky owners of amps with such devices will have trouble
servicing them with usual transistors since this will require adding
an accurate strip of external diodes although this solution works very well
once they are correctly selected.
 
The lucky owners of amps with such devices will have trouble
servicing them with usual transistors...

Note that other ThermalTrak transistors are still available so it should be possible to repair most amps. It is just the NJL4*** that are discontinued and these are the ones with best performance in every area. DIYAudio is full of perfectionists so I expected they would like to be warned.

Good thing then that I stuck with my SOT23 temp sense solution in the e-Amp. And with the NTC augmented 2 point calibration, it's really accurate and stable as well. :)

Why did you do it that way? Your solution and ThermalTrak can both work well but yours seems a less obvious choice.


Best wishes
David
 
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I got it working quite well on my Ovation 250 amp and it's been refined on th e-Amp and is now very good. I have taken a different tack to that recommended by RC and DS where they split the drivers from the power transistors and then sense the two separately. I put all the devices on the same heatsink and sense an output power device tab temp and use an NTC at the upper end of the operating temperature to pull Ibias back to the correct level. At ambient I have exactly 52mV across a pair of emitter resistors and at 65 C I also have 52mV. It's very stable across temp and the response is fast. There's some more detail on th technique on pages 40 & 41 of my e-Amp write up.
 
It's very stable across temp and the response is fast. There's some more detail on th technique on pages 40 & 41 of my e-Amp write up.

Yes, I read and appreciated the write up. I like to learn from comparison of different methods so I was curious as to why you went that way. You think it superior to the ThermalTraks in performance? or because you had already developed it earlier so it was simpler just to reuse it? Or you didn't want to use a part without a second source;)

Best wishes
David

BTW In the earlier Ovation amp you mentioned later Miller Input Compensation trials. Any write-up on that?
 
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I just continued to use what I had found worked quite well on the Ovation 250, although at the upper end of the temp range it was not tight enough on that amp, hence the NTC solution. I have been considering the Thermal Trak, but this DOD announcement worries me a bit.

Re the MIC: no, I ended up going with TMC. On my next big amp, I will do MIC as A comp option sling with TMC and MC. Will all be relay switched though.
 
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but this DOD announcement...

Re the MIC: no, I ended up going with TMC. On my next big amp, I will do MIC as A comp option sling with TMC and MC. Will all be relay switched though.

DOD?
ThermalTrak should have better dynamic behaviour but your method looks exemplary in other respects so it may be an academic point.

...as A(a?) comp(ensation) option sling(link?)
TMC does not preclude MIC so you could have had even more to try! The combination looks to have promise. MIC is especially suited to the complementary symmetrical IPS that you prefer (me too).

Best wishes
David
 
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DOD = semiconductor industry terminology for end of life.

Thermal Trak should be very good. The sense diode is co-located on the header with the transistor die. However,I have not tried them.

Unfortunately, iPad spell checker is a bit too vigorous some times and I am lazy and don't read what I write before hitting the send button.

Should read "I will do MIC as a comp option along with TMC and MC"
 
I think its a very simple reason - the market is limited, high power amps are all going class D, and indeed a lot of the market is. The true hifi sector of the market is growing smaller all the time.
Yes. I think so, too.
Maybe only Semelab - the supplier for Naim Audio about
TT electronics Semelab
will offer audio power devices (both BjT and MOSFET) suited for analog audio amps (Class A and AB) for many years.
This means, I must delete post #1 about
http://www.diyaudio.com/forums/soli...istor-families-audio-power-output-stages.html
in few years.
 
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you will find that the 4 series droop earlier as the IC increases.

Yes, not much in it since the 4 series droop a little earlier but start a little better. So percent variation is a little worse but Hfe @ 25C dips below a convenient 100 at practically identical currents.
I plan to run a half dozen in parallel so I hadn't checked past 5 amps and when Hfe is so variable it's probably academic but I will stand corrected.
Probably should admit the 1/0 series, (not 3 series) are lower capacitance to avoid another comment.
So the 4 series are only faster, more robust, more gain and have lower thermal resistance for better thermal stability and power capacity.

Best wishes
David
 
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Yes. I think so, too.
Maybe only Semelab - the supplier for Naim Audio about
TT electronics Semelab
will offer audio power devices (both BjT and MOSFET) suited for analog audio amps (Class A and AB) for many years.
This means, I must delete post #1 about
http://www.diyaudio.com/forums/soli...istor-families-audio-power-output-stages.html
in few years.

Indeed as class D is now available with feedforward correction ( with a 1 watt super low thd superfast class A) the linear power amps will become obsolete. A class D operating at at least 500 kHz sampling cannot produce non linear distortion rather distortion in class D are timing errors and at very low input inaccuracies ( overdrive must be prevented with limiters) insofar input noise produces not noise in output but distortion. This is cleverly compensated with feedforward. Another negative point is class D cannot have any CMRR. Nevertheless, the era of linear power amps is nearly over. Class D is so much cheaper and the only design objective is minimize timing error. nevertheless semiconductor is all about temperature and here class D has another advantage, there is for all semiconductors an optimum crystal temp where switching speed is a maximum. This is rather sharp for BJts and rather flat for FETs. Insofar, linear amps work best if junction temps were constant. As this is impossible to achieve , an approximation is operating setup constant. Insofar thermal trak should be better than the lagging thermal compensation. The very best is still the Quad 303 as it holds op constant on the fly there is no time lag.

Btw if anyone knows where to get a few NJL4302/4281 please let me know.
 
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