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It is currently 16 Nov 2018, 03:32

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PostPosted: 07 Oct 2018, 14:50 
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Joined: 23 Feb 2017, 02:02
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Oh hey thanks I chekced those out on rs components, they are 114nzd for 60 pairs approx.
Way off my budget but for some hifi high votlage pre amps or some high quality head amps those look very sexy.

The capacitance is so low and frequency response so high its virtualy a TO-92 deivce with 7w of max power disipation so nice.

However I do find a plorbem though, the frequency response is dropping rappidly past 0.1amps of current, this means I can't use these for output stage of head amp. This limits this device to being usefull for gain stages and high quality high votlage pre amps.


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PostPosted: 07 Oct 2018, 16:19 
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Joined: 26 Dec 2016, 03:46
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Location: Bayarea
The one you show is very low power TO126 also, I assume it's for pre-drivers.

Here are some choices https://www.digikey.com/products/en/discrete-semiconductor-products/transistors-bipolar-bjt-single/276?k=transistor&k=&pkeyword=transistor&pv1291=2526&pv1291=2113&pv1291=9545&pv1291=2524&pv1291=10608&pv1291=146&pv1291=5531&sf=1&FV=ffe00114%2C1140050%2C1280001%2C1280002%2Cdf0000a%2Cdf0000c%2Cdf00098%2Cdf00002%2Cdf000d3%2Cdf00017%2Cdf00018%2Cdf00019%2Cdf0001a%2Cdf00003%2Cdf0001e%2Cdf0001f%2Cdf0013a%2Cdf0013b%2Cdf0013e%2Cdf00025%2Cdf00026%2Cdf00027%2Cdf00004%2Cdf00005%2Cdf00036%2Cdf0003a%2Cdf0003b%2Cdf0003e%2Cdf0003f%2Cdf00040%2Cdf00044%2Cdf00045%2Cdf00046%2Cdf00047%2Cdf0004a%2Cdf0004b%2Cdf0004f%2Cdf00050%2Cdf0005b%2Cdf0005f%2Cdf00060%2Cdf00061%2Cdf00062%2Cdf00063%2Cmu150V%7C2103%2Cmu160V%7C2103%2Cmu170V%7C2103%2Cmu175V%7C2103%2Cmu180V%7C2103%2Cmu185V%7C2103%2Cmu200V%7C2103%2Cmu220V%7C2103%2Cmu225V%7C2103%2Cmu230V%7C2103%2Cmu250V%7C2103&quantity=&ColumnSort=0&page=1&stock=1&pageSize=25

I use the 2SC4883https://www.digikey.com/product-detail/en/sanken/2SC4883A/2SC4883A-ND/3929415

I would be a lot more comfortable using TO220.


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PostPosted: 07 Oct 2018, 21:59 
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Joined: 23 Feb 2017, 02:02
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https://www.aliexpress.com/store/produc ... 7228bkZAzn
I was going to try some of these since I had been getting geniune tip35c from this seller.
Toshiba transistors have the chips made in Japan then assembled in China, same with ST micro and on semi.

But buying from RS was cheaper in terms on quantaty.
I alrady have too many tip35c precisley mathced pairs lieing arround theres already no going back in terms of swapping to HF transitors for power amps

If you search audio in this store you can find plenty of high frequency transitors


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PostPosted: 08 Oct 2018, 01:33 
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Joined: 26 Dec 2016, 03:46
Posts: 158
Location: Bayarea
That's good price. But I already have over 100 of each already. I use it as pre-drivers, only use two each for each amp, I am good for the rest of my life!!! For a while, they are not available, so when I found them in a reputable place, I bought by volume.


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PostPosted: 24 Oct 2018, 02:43 
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Joined: 23 Feb 2017, 02:02
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Unfortunaltey I'm getting fakes from RS Components, sure the KSD882 are made in south korea with geniune priting, craftmanship and power ratings, but the transfer frequency is not up to specs of 80MHZ at 0.1A.
Its arround 2-10MHZ max, worse than fake TIP41C from china.


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PostPosted: 24 Oct 2018, 03:09 
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Joined: 23 Feb 2017, 02:02
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I might try my luck with geniune tip31c from rs components, smaller power disipation deffintlley higher maximum frequency.
Or I might go aliexpress for some hopefully geniune japanese transitors


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PostPosted: 24 Oct 2018, 23:55 
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Joined: 26 Dec 2016, 03:46
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Location: Bayarea
How do you test for fT?


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PostPosted: 25 Oct 2018, 21:38 
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Joined: 23 Feb 2017, 02:02
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We replaced the output transistors which were a massive draw back on the 4 stage amp, then refine the compensation capacitors to get higher frequency response.

The system became unstable and outright frequency response is about 30% worse less than with TIP41c.

We did make excatly same op amp but with TO-92 output transistors.
The frequency response went off the roof like no voltage reduction at 1MHZ and distortionless response on scope looking by eye.
The slew rate is 188v/uS into 4k7 load


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PostPosted: 25 Oct 2018, 22:13 
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Joined: 26 Dec 2016, 03:46
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Location: Bayarea
I don't think you can say the fT of the new transistor is lower just because you put into your circuit and get worst response, There are a lot of factors like input and output capacitance that affect the frequency response of the amp.

Another thing you have to be careful, you use vector board and wire up the circuits, you have long runs, that will become an inductor at close to fT of the transistor. If you push the fT, you have to be a lot more careful in layout, the way you probe the circuit, termination and transmission line effect. This is way beyond AF amplifier. If you look at my pcb layout, it's layout for RF into over 100MHz. Every collector of the big transistors has it's own 0.1uF parallel with 10uF bypass cap to ensure the collector doesn't see inductance. If it is done right, the faster the transistor( to a certain point, I won't go for anything over 300MHz), the better, just have to do it with RF knowledge.

I design high speed and microwave circuits, even at 50MHz, it's a totally different world. You can't use scope probe with ground leads. My experience with circuit of 50MHz and over is if you don't see the result you expect, 50% chance is the way you measure it.

I heard of RS components, I don't think they would sell you fake transistors. I question the way you test the transistors.


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PostPosted: 25 Oct 2018, 22:26 
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Joined: 26 Dec 2016, 03:46
Posts: 158
Location: Bayarea
Another thing, 1MHz response on your type of low power amps is believable. 188V/uS is not. This means for 2V transition, it's 10.6nS. That's too fast for these kind of audio circuit regardless of load. I think you might be seeing ringing or some other effect. As I said, when you get into MHz, layout becomes important, your vector board and long leads is not going to work. If I can still find some of the old bread board circuit that work in 10 to 50MHz region, I'll take a picture to show you, it's a completely different technique and mentality in breadboarding.


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