Small signal Mosfet AB PA? - 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 12th February 2010, 02:10 AM   #1
diyAudio Member
 
Join Date: Oct 2007
Default Small signal Mosfet AB PA?

I wanted to build a low wattage class AB PA using BS170 and BS250... could this be possible, using max voltage with bipolar power? Maybe could exeed current rattings... well, just an idea.
  Reply With Quote
Old 12th February 2010, 03:23 PM   #2
Bigun is offline Bigun  Canada
diyAudio Member
 
Bigun's Avatar
 
Join Date: Jan 2009
Blog Entries: 2
I'm not familiar with these devices, can you tell us more about them ?

From my perspective, I don't see why you can't build something along the lines of 'just do it'
__________________
"The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed." Robert M Pirsig.
  Reply With Quote
Old 12th February 2010, 06:04 PM   #3
satoru is offline satoru  United States
diyAudio Member
 
Join Date: Jan 2007
Location: Berkeley, California
BS170 is a 60V 0.5A MOSFET. Max power dissipation is 0.3W. May be you can parallel many of them to achieve your goal but you may need more than 100...

Slideman82, DIY power amplifier design starts by deciding how much power to put on what kind of load. From there, you can pick a suitable output device, heatsink, power transformer, etc. Then you can have fun meddling around on the circuit.
I design low voltage amp for my own use since I rarely need more than 2W output on 6 ohm speaker. But even for me, BS170 won't do well. Regardless, if you come up with an extraordinary design with BS170, share with us!

Have fun!
  Reply With Quote
Old 13th February 2010, 12:49 AM   #4
diyAudio Member
 
Join Date: Oct 2007
Quote:
Originally Posted by satoru View Post
BS170 is a 60V 0.5A MOSFET. Max power dissipation is 0.3W. May be you can parallel many of them to achieve your goal but you may need more than 100...

Slideman82, DIY power amplifier design starts by deciding how much power to put on what kind of load. From there, you can pick a suitable output device, heatsink, power transformer, etc. Then you can have fun meddling around on the circuit.
I design low voltage amp for my own use since I rarely need more than 2W output on 6 ohm speaker. But even for me, BS170 won't do well. Regardless, if you come up with an extraordinary design with BS170, share with us!

Have fun!
Great reply!!!!!!!! So, we could do it quasi complementary with BS250's? Load? 8 or 4 ohms...

Unfortunately I don't know how to design a PA yet...

I was thinking a bit, and the idea of using an existing PA with a small power transformer (for example, 12V dual supply and 1 or 2A) could work for me!
  Reply With Quote
Old 13th February 2010, 01:06 AM   #5
Bigun is offline Bigun  Canada
diyAudio Member
 
Bigun's Avatar
 
Join Date: Jan 2009
Blog Entries: 2
Yikes, 300mW maximum dissipation is not a good omen, it really does need dozens of them to get any meaningful power unless you want to design for some very high efficiency speakers. If you have to go buy a transformer etc. it might be worth to consider buying some power transistors. If this is acceptable you could pick out a circuit that is known to work as there are quite a few around (search for Carlos' DX amplifier and look at Nelson Pass DIY)

If you do want to use these devices - how many do you have that you can parallel up?
__________________
"The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed." Robert M Pirsig.
  Reply With Quote
Old 13th February 2010, 06:08 AM   #6
satoru is offline satoru  United States
diyAudio Member
 
Join Date: Jan 2007
Location: Berkeley, California
There is a Japanese DIYer who made a 11W amplifier with 2SA1015/2SC1815 (TO-92 300mW dissipation) as output transistors. He literally paralleled 100 each...

The web page is in Japanese but you can see the photos of the amp.

A1015/C1815_100???????????
  Reply With Quote
Old 16th February 2010, 04:21 PM   #7
diyAudio Member
 
Join Date: Oct 2007
Hahahaha 100! Great! But I want it with mosfets! I'm gonna try some nelson pass amp for sure, probably a lower voltage version of the Citation 12... just and idea.

Thanks to all!

Oh, I'd parallel as many as I needed for 2 or 5 W
  Reply With Quote
Old 16th February 2010, 04:44 PM   #8
satoru is offline satoru  United States
diyAudio Member
 
Join Date: Jan 2007
Location: Berkeley, California
Hmmm. Even for 2 to 5W output power, the output devices have to be packed in case with around 30W to 50W power dissipation and better be mounted on a heatsink. You still need around 100 devices if you stick to BS170. BS170 (and almost all other MOSFETs) has higher saturation voltage compared to BJTs (so they need higher power supply voltage) which in turn results in more power to dissipate.
  Reply With Quote
Old 16th February 2010, 05:45 PM   #9
Bigun is offline Bigun  Canada
diyAudio Member
 
Bigun's Avatar
 
Join Date: Jan 2009
Blog Entries: 2
Well, Nelson is leading the way, he has a 1,000 JFET monster under construction so 100 parts is just an appetizer
__________________
"The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed." Robert M Pirsig.
  Reply With Quote
Old 16th February 2010, 05:54 PM   #10
AP2 is offline AP2  Italy
Banned
 
Join Date: Dec 2009
Location: Italy
Hi,
What is the advantage of using n.100 BS170? on stage A-B?
  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
small-signal (small-power) fast switching complementary transistors Lola Luna Solid State 3 8th April 2010 07:51 PM
Small-signal (or small power) pentode that can handle 400V (or more)? GordonW Tubes / Valves 12 13th June 2008 02:07 AM
help!ab class mosfet amp mbonus Solid State 31 19th September 2005 04:14 PM
complementary small signal mosfet? till Parts 3 15th May 2004 04:18 PM
MOSFET small signal pairs? DrG Solid State 0 8th October 2003 05:59 AM


New To Site? Need Help?

All times are GMT. The time now is 06:26 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