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Old 29th December 2012, 12:44 AM   #21
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Quote:
Originally Posted by Stormrider View Post
...
2sa1930/2sc5171 are a good choice for medium power amps if you can get them.
...
For really high power uses the OnSemi MJE15034/35 devices work, but they are not in the same class as the 1302/3281's.
Yes. It is a pity that there is not a driver to really match the 1302/3281.
The 1930/5171 enter second breakdown too early for my plans.
Has anyone considered a FET as a driver? Seems like it may be a suitable application.

Best wishes
David
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Old 29th December 2012, 01:35 AM   #22
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2sk216 and 2sj79 were great sounding drivers in front of those, back in the '90s..
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Old 29th December 2012, 02:15 AM   #23
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These folks seem to understand lateral power FETs for audio. Wonder why they don't release a 1 Amp driver and become the go-to source:

Magnatec. ALFET Lateral MOSFETs

They don't care about your bipolar driving problems? Their 8 Amp model doesn't get linear until too high current, and has 600p input capacitance compared to 90 for the old Hitachi parts...
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Old 29th December 2012, 03:59 PM   #24
Telstar is offline Telstar  Italy
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Hitachi lateral mosfets are excellent drivers. Hard to source, though.

I saw more than one amp using the same 1302/3281 as drivers, amd then using predrivers. This with several output pairs. If you have 4 tops, it's not needed.
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Old 29th December 2012, 10:15 PM   #25
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I am interested in the potential speed of MOSFETs for use in advanced compensation schemes. So the laterals are less attractive to me, no real improvement on the 15034/35 which is my current benchmark.
Some of the verticals have ~100pF. I am not very familiar with FETs but total (gate stopper + intrinsic) resistance of 10 ohms looks reasonable so roll-off around 160 MHz, a substantial jump from the 15034/35.

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David
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Old 29th December 2012, 11:28 PM   #26
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Quote:
Originally Posted by Andrew Eckhardt View Post
...... Wonder why they don't release a 1 Amp driver and become the go-to source:
Magnatec. ALFET Lateral MOSFETs
The product is SEMELAB who also do a nice line of audio power transistors. Profusion handle the same LATFET parts with different marking and more - They are probably the "go-to" source now.
Medium Power-Driver
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Old 30th December 2012, 12:11 AM   #27
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Originally Posted by fab View Post
....I could not find the option to select the "E" suffix for 100 to 200 HFE range....Fab
Sadly, this option for through-hole parts is disappearing too. Even JFETs have almost vanished since Fairchild cut production of many US types. I can only suggest buying stocks to last into the forseeable future, if they become available as this is a sure sign of obsolescence. I really don't like the option of building anything new based on NOS or high-risk fake parts.

I have to sort my low-med power transistors for Hfe now too. That's why the parts selected must be cheap and designs need to be centred on the available range. However, I don't think you will have problems getting a good yield with 100-200 spec.
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Old 30th December 2012, 03:12 AM   #28
fab is offline fab  Canada
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Quote:
Originally Posted by Ian Finch View Post
The product is SEMELAB who also do a nice line of audio power transistors. Profusion handle the same LATFET parts with different marking and more - They are probably the "go-to" source now.
Medium Power-Driver
Thanks for the link to Profusion. However,the web site states : "For a lateral MOSFET amplifier you are better served with Sanyo's 2SA1209/2SC2911. Why? The low output capacitance (Cob) of these devices translates to reduced "Miller" effect, resulting in lower distortion..."
But the table of transistor provided does not include the 2SA1209/2SC2911 nor using the search engine...

Fab
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Old 30th December 2012, 09:59 AM   #29
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OnSemiconductor owns Sanyo Semiconductor now and the 2SA1209/2SC2911 is EOL:
ON Semiconductor (some stock)
ON Semiconductor
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Old 31st December 2012, 12:04 AM   #30
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I favor building a ROBUST solid state amp that will not self-destruct with a 1-ohm load. I make sure that no transistor exceeds its spec's with a 1-ohm load in both Spice and on-bench testing.

Triple T Class-AB with low Class-A bias Output Stage:
--- output: NJL3281D NPN, NJL1302D PNP
--- driver: MJE15034 NPN, MJE15035 PNP -- do not destruct with 1 ohm load
--- VAS Hawksford Enhanced Cascode or standard Cascode: Low Voltage High Beta signal driver BC560C or 2SA970 PNP, BC550C or 2SC970 NPN. High Voltage Cascode 2SC3503 NPN and 2SA1381 PNP

I want to protect my speakers over my amplifier. Instead of putting a SPEAKER-CONNECT-RELAY in series between the amp output stage and speakers I have my "safe operation" protection circuits control a LARGE MOSFET with a 1ohm shunt resistor connected to the amp output terminals. If DC is detected, or if the output signal does not closely follow the input signal the MOSFET+1ohm is shunt connected and AC power disconnected to protect the speakers.

Save the Planet! Go Green! For low Class-A bias with Class-AB Output Stages I favor using ThermalTrak NJL3281D (NPN) and NJL1302D (PNP). The thermal diode really does reduce thermal transient distortion, especially for the first 30 minutes after turn-on.

For high Class-A bias, high power Class-AB amps with many output transistors pairs where fast Vbe thermal transisents do not occur the Sanken NPN 2SA1216 and Sanken PNP 2SC2922 have superior sound and thermals.
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Last edited by LineSource; 31st December 2012 at 12:14 AM.
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