Comparison Of Onsemi Vs Toshiba Transistor - diyAudio
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Old 23rd August 2007, 11:45 AM   #1
fotios is offline fotios  Greece
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Default Comparison Of Onsemi Vs Toshiba Transistor

In this thread i wish to put in comparison the small signal transistor of Toshiba vs. OnSemi. I ask from anyone it knows well these types to say his opinion. I will request you do not write hasty thoughts and you take into account all the parameters: hFE, Ft, especially the Vce breakdown the Ic and the Pd. If you want take a look in the datasheets of Toshiba and OnSemi
Given:
1) They are to operate in a power amplifier with a supply of +/- 70Vd.c. and thus Vpp = 140Vd.c.
2) The Ic will be at least 10mA
Comparison:
2SC2240 vs. 2N5551
2SA970 vs. 2N5401
Thanks in advance
Fotios
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Old 23rd August 2007, 12:00 PM   #2
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You don't want them to dissipate 0.7W, do you?
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Old 23rd August 2007, 03:04 PM   #3
fotios is offline fotios  Greece
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Quote:
Originally posted by darkfenriz
You don't want them to dissipate 0.7W, do you?
Of course not. One further explanation it is that those will operate in small signal stages, as in the difference amplifier, in current mirror, and constant current sources (except than the CCS of VAS) where the current it does not exceeds 15 to 20mA. Also it must be noted that i have big experience with all types of OnSemi devices; but with those of Toshiba almost nothing!
Thus this is not - believe me! - a trick question.
Fotios
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Old 23rd August 2007, 03:39 PM   #4
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Toshiba's have higher gain, and less Beta spread making matching MUCH easier.
Your Onsemi parts can have more current though.
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Old 23rd August 2007, 09:11 PM   #5
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With 70V at collector you should not have more collector current than 3mA from toshibas and probably 6mA from onsemis. These to92 devices have really low maximum power dissipation, 0.3W for 2sa970/c2240 and 0.6W for 2n5401/5551, so I'd choose the latter.
If you need more current, like 15mA, then check 2sa1360/c3423 from toshiba.

BTW. My experience with a970/c2240 is bad, beta lower than it should, strange fults, maybe I had some fakes.
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Old 23rd August 2007, 09:12 PM   #6
fotios is offline fotios  Greece
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Quote:
Originally posted by QSerraTico_Tico
Toshiba's have higher gain, and less Beta spread making matching MUCH easier.
Your Onsemi parts can have more current though.
I know very well that you wrote. The benefits of Toshiba compared to OnSemi are mainly the higher hFE from 200 to 700, instead OnSemi from 60 to 250. I don't have problem to match them, because i use in the input a scheme with single difference amplifier loaded with current mirror; the current mirror by balancing the collector currents of difference amplifier transistors, it eliminates the D.C. offset in output and thus the need to matching these. This is my own opinion of course, because i consider that other beneffits caused from matching it is of small importance in practical circuits. The other benefit of Toshiba it is the smallest relativelly Cob of 4pF in comparison with the 6pF of OnSemi but again the difference it is unimportant in practice. As for the ft it is almost the same for the two, at 100MHz. On the other hand the main benefits of OnSemi are the higher Vce of 150V instead Toshiba's 120V, and the higher Ic of 600mA instead Toshiba's 100mA and thus the higer Pd. One point which seems to not interests OnSemi it is the absence of a noise figure, instead Toshiba gives this parameter as 2 to 6dB.
For many years i use the pair MPSA06-MPSA56 in amplifiers with supply up to +/-60Vdc, and from +/-70Vdc and above the pair 2N5401-2N5551 with success. Many people in this forum it prefers the Toshiba devices and this cause to me questions if my amplifier will be heared better with the substitution of OnSemi devices in small signal stages from Toshiba's. The purpose it is perhaps there is a further improvement of amplifier in noise and bandwidth. From the other hand, i can not say that the quality of sound it is simple good with the use of OnSemi devices; indeed the amplifier has verry good performance. I have obsered certainly, that as the supply voltage increased as much better heared the amplifier concretely with the pair of 2N5401-2N5551. I have achived with supply of +/-80Vdc and above a rise time of 1,7 to 1,8 žsec under 50% of full output swing; this is translated in a bandwidth of 300:1,8=167KHz at 200Wrms. In small signal i have achived rise times of 1,3 to 1,4 žsec! Thus a bandwidth more than 200KHz. And all of these with compensated Cdom with 100pF. And with usual output transistors such as MJ15003-MJ15004 or MJ15024-MJ15025.
This is my question to you: It is worth the substitution of OnSemi transistors with Toshiba's under so high supply levels? Of course i ordered some pairs of Toshiba to make an experiment if there is a difference in performance.
For the pair MPSA06-MPSA56 with a supply of +/-60Vdc i have achived a worse rise time of 1,9 to 2,0 žsec. I believe strongly that as much higher the supply voltage as better the performance of an amplifier. Unfortunatelly the vast majority of members it is engaged with amplifiers of +/-40Vdc supply as much and does not has experience with the situation of supply levels above +/-70Vdc.
Any further comment from persons with such experience it is well appreciated.
Thanks in advance
Fotios
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Old 23rd August 2007, 09:17 PM   #7
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2sc2240 and 2sa970 are much better for audio.

mpsa
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Old 23rd August 2007, 09:22 PM   #8
aandy is offline aandy  United Kingdom
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I have built 10's of thousands of amps with tosh
mpsa
also 2sc2713
2sa1163
smt option's
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Old 23rd August 2007, 09:23 PM   #9
fotios is offline fotios  Greece
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Quote:
Originally posted by darkfenriz
With 70V at collector you should not have more collector current than 3mA from toshibas and probably 6mA from onsemis. These to92 devices have really low maximum power dissipation, 0.3W for 2sa970/c2240 and 0.6W for 2n5401/5551, so I'd choose the latter.
If you need more current, like 15mA, then check 2sa1360/c3423 from toshiba.

BTW. My experience with a970/c2240 is bad, beta lower than it should, strange fults, maybe I had some fakes.
Also me i fear the Toshiba's from the view of origin (maybe this was your problem, instead OnSemi it is trasty because it is printed on the device ; thus you can based on the datasheet of the device during a drawing and without the transistors yet in your hands. Also OnSemi has authorized distributors at least in all countries of Europe and you know what you buy exactly. I have not see this yet in any Toshiba's small signal transistors.
Thanks
Fotios
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Old 23rd August 2007, 09:26 PM   #10
fotios is offline fotios  Greece
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Quote:
Originally posted by aandy
I have built 10's of thousands of amps with tosh
mpsa
also 2sc2713
2sa1163
smt option's
Of which supply level? If you prefer of which output power?
Thanks
Fotios
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