I was going to tell you to search, but then I did it and nobody had used them yet and reported back about it. I did find one interesting application note where the temperature monitoring was done with the inbuilt diodes in series on paralleled transistors, but that's about it.
somebody actually HAD some of these, but didn't report back what they did with them...?
somebody actually HAD some of these, but didn't report back what they did with them...?
Heres an apllication note on using these in a power amplifier.
http://www.onsemi.com/pub/Collateral/AND8196-D.PDF
http://www.onsemi.com/pub/Collateral/AND8196-D.PDF
Interesting devices!
Diode that senses the temperature, like a transistor in a VBE multiplier,
has its own 2 pins.
So the ThermalTrak is a 5 pins device.
See attached image.
----------------------
Complementary ThermalTrak™ Transistors
NJL3281D(NPN) NJL1302D(PNP)
BIPOLAR POWER TRANSISTORS
TO-264, 0.625 °C/W
15 A, 260 V, 200 W
fT 30 MHz
http://www.onsemi.com/PowerSolutions/product.do?id=NJL1302D
Diode that senses the temperature, like a transistor in a VBE multiplier,
has its own 2 pins.
So the ThermalTrak is a 5 pins device.
See attached image.
----------------------
Complementary ThermalTrak™ Transistors
NJL3281D(NPN) NJL1302D(PNP)
BIPOLAR POWER TRANSISTORS
TO-264, 0.625 °C/W
15 A, 260 V, 200 W
fT 30 MHz
http://www.onsemi.com/PowerSolutions/product.do?id=NJL1302D
Attachments
Unfortunately they don't seem to be optioned for free sampling.
I wonder how well they match off with standard MJL3281/1302? Since most amplifier designers will go with a VBE multiplier (and perhaps use several output transistors in parallel), maybe it will be viable to get just one NJL device, use its thermal diode for bias tracking, and use standard MJL stuff for the rest - cost savings, assuming these transistors are reasonably matched...
Cheers!
Clem
I wonder how well they match off with standard MJL3281/1302? Since most amplifier designers will go with a VBE multiplier (and perhaps use several output transistors in parallel), maybe it will be viable to get just one NJL device, use its thermal diode for bias tracking, and use standard MJL stuff for the rest - cost savings, assuming these transistors are reasonably matched...
Cheers!
Clem
Hi Clem,
Good thought for a manufacturer who wants to mystify the average service person. It adds a skew to the inventory and may become unavailable. Standard methods are reliable and so most manufacturers will be reluctant to use them.
If it's needed to track temperature that closely in an amplifier, I feel it's a marginal design.
Now if a replacement from NTE shows up ... Sad state of affairs for many repair shops.
-Chris
Good thought for a manufacturer who wants to mystify the average service person. It adds a skew to the inventory and may become unavailable. Standard methods are reliable and so most manufacturers will be reluctant to use them.
If it's needed to track temperature that closely in an amplifier, I feel it's a marginal design.
Now if a replacement from NTE shows up ... Sad state of affairs for many repair shops.
-Chris
Hi Chris,
Actually it seems a good idea to put the diode into the package, (check Doug Self's site and book - he's done some studies on the issue of thermal tracking) - seems there's quite a bit of thermal lag using the more usual mounting methods. Self recommends mounting the sensor (assuming plastic pack output transistors) on the front (plastic) of the outputs, as this actually heats up faster and is a better representation of the die's temp.
I guess if one is really trying to keep his outputs optimally biased (exactly Class B, avoiding gm doubling) this would be worth a try...
Yeah, you're right about having to deal with more parts!!
Cheers
Clem
Actually it seems a good idea to put the diode into the package, (check Doug Self's site and book - he's done some studies on the issue of thermal tracking) - seems there's quite a bit of thermal lag using the more usual mounting methods. Self recommends mounting the sensor (assuming plastic pack output transistors) on the front (plastic) of the outputs, as this actually heats up faster and is a better representation of the die's temp.
I guess if one is really trying to keep his outputs optimally biased (exactly Class B, avoiding gm doubling) this would be worth a try...
Yeah, you're right about having to deal with more parts!!
Cheers
Clem
I'm the one with a bunch of the ThermalTraks. Things are going slow as I have a bunch of things to do (besides work). However, I am happy to say that my first prototype is almost ready. Preliminary measurements and listening tests show it to be pretty good.
I'll share more soon. Stay tuned. I did ask in a previous post if there were any interest in the ThermalTraks.
Price-wise, they're expensive at Digikey. OnSemi's volume quote is cheap at $2.20 but Digikey sells them for like $7.
I'll share more soon. Stay tuned. I did ask in a previous post if there were any interest in the ThermalTraks.
Price-wise, they're expensive at Digikey. OnSemi's volume quote is cheap at $2.20 but Digikey sells them for like $7.
Arius said:
One thing I have thought about, when using a BD139 in diode configuration
or some other diode,
for using mV base-emitter drop to measure temperature.
How much current is good to run through them?
Should not be too much, it will make them warm themselves.
But not too little.
Is this a trial and error situation or are there any good target values?
Lineup,
I'd treat the BD139 as a silicon PN junction diode. In that case, excite it with 10uA. You should get about 2.3mV/degC sensivity with that.
Since we're talking about power amps, many amps do not use the typical BD139 mounted on the heatsink to sense temp per se. Rather, as you probably already know, it is used as an amplified VBE generator which then biases the output stage while compensating for temperature.
The ThermalTraks are supposed to replace this temp dependent bias generator circuit (their internal diodes, that is).
I'd treat the BD139 as a silicon PN junction diode. In that case, excite it with 10uA. You should get about 2.3mV/degC sensivity with that.
Since we're talking about power amps, many amps do not use the typical BD139 mounted on the heatsink to sense temp per se. Rather, as you probably already know, it is used as an amplified VBE generator which then biases the output stage while compensating for temperature.
The ThermalTraks are supposed to replace this temp dependent bias generator circuit (their internal diodes, that is).
thanks Arius
Yes, I was thinking in pure heatsink temp measuring 'sensor',
maybe with some LEDs to show how warm a Class A is.
With the last LED lighting when amp has reached full working temp.
Now I know the sensor only takes a very little current.
I will probably use another 'sensor' to set room temperature as a zero level reference.
One interesting fact with heatsinking Class A:
The more power output ( across load )
the less power and heat in output transistors and heatsink.
Heatsink is as coldest, when playing at maximum Watt power!
Yes, I was thinking in pure heatsink temp measuring 'sensor',
maybe with some LEDs to show how warm a Class A is.
With the last LED lighting when amp has reached full working temp.
Now I know the sensor only takes a very little current.
I will probably use another 'sensor' to set room temperature as a zero level reference.
One interesting fact with heatsinking Class A:
The more power output ( across load )
the less power and heat in output transistors and heatsink.
Heatsink is as coldest, when playing at maximum Watt power!
Or, just use one of those cpu temp sensors from a dead semi-modern motherboard - these are temperature-dependent resistors, and usually have about 10K ohms at 25 deg C. May not need amplification anymore since the R change versus temp would be large... They are pretty linear I think... you can find these on power-supply fans that change speed with temp of air (though some use a diode)...
Cheers!
Clem
Cheers!
Clem
Has anyone tried this Jaycar amp module yet:
![IMGDEAD]](/community/proxy.php?image=http%3A%2F%2F%5BIMGDEAD%5Dhttp%3A%2F%2Fimg151.imageshack.us%2Fimg151%2F9190%2Fkc5470ti7.png%5B%2FIMGDEAD%5D&hash=43656c04549b8f1963b869c5e913958a)
more about ThermalTrak output devices
http://www.clarisonus.com/blog/?p=55
http://www.planetanalog.com/features/power/showArticle.jhtml?articleID=57700271
http://www.tubecad.com/2006/10/blog0084.htm
more about ThermalTrak output devices
http://www.clarisonus.com/blog/?p=55
http://www.planetanalog.com/features/power/showArticle.jhtml?articleID=57700271
http://www.tubecad.com/2006/10/blog0084.htm
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