Toshiba Power Mosfets 2SK3497/2SJ618 - A little testing - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 4th May 2010, 03:34 PM   #1
soekris is offline soekris  Denmark
diyAudio Member
 
Join Date: Jun 2009
Default Toshiba Power Mosfets 2SK3497/2SJ618 - A little testing

I have several times expressed that I like the Toshiba 2SK3497/2SJ618 power mosfets that, although they're not that new, haven't been used much and especially not in DIY, partly because nobody seems to stock them....

So finally I received my 100 pairs from Digikey, although it took a long time to get them.

My main interest is using them without global feedback so I'm concentrating on measuring how linear they are, also at high frequencies, what the output impedance will be and how fast they are.

I have an amplifier breadboard testbench with exchangeable output stages and have done some measurement to find out how good they are. To have something to compare with I have done the same measurements with the best Bipolars (OnSemi NJW3281/NJW1302 with KSC2690/KSA1220 drivers) and Hitachi style lateral mosfets (Semelab BUZ900/BUZ905).

All measurements are done with a fast jfet input folded cascode voltage amplifier with an output impedance of 3.4 Kohm, with no global feedback, and with a single set of output devices. 0db reference is at 17V RMS into 8 ohm, 1 db below clipping of the driver stage.

First are the Bipolars, looks pretty good with THD at 0.3% and quickly going down at lower levels, with an output impedance of 0.4 ohm and power bandwidth of 900 Khz. I have used 0.22R emitter resistors, so half the output impedance are from those. You can expect results to be consistent when paralleling more output pairs, which will result in lower output impedance. Bias is set at 100 mA, and higher will improve lower level performance, keeping them in class A further up.

Next is the Hitachi style mosfets, THD is significant higher, close to 1%, but most of it is 2nd harmonic. Output impedance is 1.2 ohm, with 0.1R source resistors. Paralleling more pairs will really help, both on output impedance and THD as they are due to the unlinear and low Yfs. Bias is set at 100 mA and higher will improve significant on performance and the working point moves closet to their linear operating point, sweet spot is probably 3-5 pairs and 200 mA bias per pair. Without current drivers the power bandwidth is 180 Khz, and THD increases at higher frequencies, but not that much. Cgs is dominant over Cgd so paralleling more will not change the high frequency performance that much, with a little higher drive current in the voltage amplifier they will work fine without extra current drivers.

And now the Toshiba power mosfets. THD with 100 mA bias don't look to good but are mostly 2nd harmonic. Output impedance is 0.35 ohm with 0.1R source resistors, close to the Bipolars thanks to their high Yfs. But with higher bias they really shine, 300 mA get them into the linear range and now they look very good. But power bandwidth is only 132 Khz and THD increases with frequency, reaching 1% at 20 Khz. As Cgd is dominant over Cgs then paralleling more pairs will just make it worse. A single pair could be used with higher drive current, but a current driver stage is really needed for good results, then the power bandwidth goes up to 730 Khz and THD don't raise with frequency. With a current driver stage you can also lower current in the voltage amplifier stage, ending with THD <0.2% at 1 db below full power.

My conclusion are that the Toshiba power mosfets could be a good fit to make a great non feedback amplifer, assuming a current driver stage and 300 mA bias per pair.

The bipolar are also good, and have the advantage that you don't need to match them when paralleling, unlike the mosfets.

The Hitachi style laterals mosfets really needs to be used in amplifiers with feedback.

The names of the attached THD curves should explain what they are, but basically they follow the text.

Soren
Attached Images
File Type: png 17Vrms_Bipolar_100mA_8R.png (4.6 KB, 1653 views)
File Type: png 17Vrms_Hitachi_100mA_8R.png (4.6 KB, 1616 views)
File Type: png 17Vrms_Hitachi_200mA_8R.png (4.7 KB, 1599 views)
File Type: png 17Vrms_Hitachi_300mA_8R.png (4.8 KB, 1598 views)
File Type: png 17Vrms_Toshiba_100mA_8R.png (4.5 KB, 1585 views)
File Type: png 17Vrms_Toshiba_200mA_8R.png (4.6 KB, 165 views)
File Type: png 17Vrms_Toshiba_300mA_8R.png (4.7 KB, 163 views)
File Type: png 17Vrms_Toshiba_100mA_8R_Freq.png (4.2 KB, 177 views)
File Type: png 17Vrms_Toshiba_100mA_Driver_8R_Freq.png (4.0 KB, 229 views)
File Type: jpg Test_Setup.jpg (619.0 KB, 549 views)

Last edited by soekris; 4th May 2010 at 03:36 PM.
  Reply With Quote
Old 5th May 2010, 10:50 PM   #2
mlloyd1 is offline mlloyd1  United States
diyAudio Member
 
mlloyd1's Avatar
 
Join Date: Feb 2001
Location: illinois
thanks for supplying the test data.
just for completeness, what was distortion readings and bandwidth without an output stage attached (i.e. the driver alone)?

mlloyd1
  Reply With Quote
Old 5th May 2010, 11:20 PM   #3
soekris is offline soekris  Denmark
diyAudio Member
 
Join Date: Jun 2009
Quote:
Originally Posted by mlloyd1 View Post
just for completeness, what was distortion readings and bandwidth without an output stage attached (i.e. the driver alone)?
-3db Power Bandwidth without output module and just the 3.4K load is about 1 Mhz, but there might be some extra capacitance due to the breadboard design....

THD versus Power, again with 0db at 17V rms. All test were run with +- 30V from my lab power supply.
Attached Images
File Type: png 17Vrms_DriverOnly_3K4.png (4.8 KB, 511 views)
  Reply With Quote
Old 21st September 2010, 06:28 PM   #4
diyAudio Member
 
tiefbassuebertr's Avatar
 
Join Date: Jul 2005
Location: D-55629 Schwarzerden
are there p-spice parameters online?
  Reply With Quote
Old 22nd September 2010, 01:33 AM   #5
soekris is offline soekris  Denmark
diyAudio Member
 
Join Date: Jun 2009
Quote:
Originally Posted by tiefbassuebertr View Post
are there p-spice parameters online?
Not that I know of, but I haven't looked that much, prefer to play with actual hardware :-)


Soren
  Reply With Quote
Old 27th October 2010, 08:07 PM   #6
diyAudio Member
 
tiefbassuebertr's Avatar
 
Join Date: Jul 2005
Location: D-55629 Schwarzerden
Quote:
Originally Posted by soekris View Post
Not that I know of, but I haven't looked that much, prefer to play with actual hardware :-)
Soren
Toshiba send me "Level 3" p-spice parameters
Attached Files
File Type: txt 2SJ618 P-Spice.txt (1.5 KB, 299 views)
File Type: txt 2SK3497 P-spice.txt (1.5 KB, 198 views)
  Reply With Quote
Old 5th May 2012, 08:20 PM   #7
Telstar is offline Telstar  Italy
diyAudio Member
 
Join Date: Dec 2007
Location: Italy
great threat, thanks!!!
__________________
"The total harmonic distortion is not a measure of the degree of distastefulness to the listener and it is recommended that its use should be discontinued." D. Masa, 1938
  Reply With Quote
Old 16th October 2014, 12:45 PM   #8
ilimzn is offline ilimzn  Croatia
diyAudio Member
 
Join Date: Feb 2005
Location: Zagreb
These measurements should really be done with a very low output impedance driver, as input capacitances are nonlinear (especially in the MOSFET case) and a lot of distortion can be generated by this mechanism, especially crossing the class A/B treshold.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
testing a bank of mosfets Pbassred Solid State 1 5th December 2007 10:37 AM
testing L-Mosfets whalefat Solid State 13 14th June 2005 12:42 AM
Testing Hitachi Mosfets Zero Cool Solid State 11 5th October 2004 11:01 AM
Request for assistance - where can I buy Toshiba MOSFETs in US? thoriated Solid State 2 3rd December 2003 04:48 PM
Wierd science and testing Mosfets Zapped Pass Labs 7 26th November 2002 06:33 PM


New To Site? Need Help?

All times are GMT. The time now is 08:59 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2