Simply because in my mind IRF640=low to medium power fet....but it seems that i am false...
Could you share your work on shematic and layout?
Marc
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have you ever seen this?
http://sjostromaudio.com/dudek_files/DPA-386.pdf
this is amp from Pavel DUDEK - one pair IRF in TO220 at 100W is enough
shematic and layout of V50 (amp on pictures) will be free on trunek´s web
http://sjostromaudio.com/dudek_files/DPA-386.pdf
this is amp from Pavel DUDEK - one pair IRF in TO220 at 100W is enough
shematic and layout of V50 (amp on pictures) will be free on trunek´s web
For bias stability with irf/irfp version the best is to use n-channel mosfet in biasing ciruit.
With bd139 bias from cold 100mA is dropping to around 60-70mA when hot but with eg. irf840 (in my case) bias for o/p transistors is rock solid in wide temerature range.
Also I am not sure if the source resistors for one pair o/p transistors (irfp240/9140) are required - I am running amp without them and everythink looks just fine.
Regards
With bd139 bias from cold 100mA is dropping to around 60-70mA when hot but with eg. irf840 (in my case) bias for o/p transistors is rock solid in wide temerature range.
Also I am not sure if the source resistors for one pair o/p transistors (irfp240/9140) are required - I am running amp without them and everythink looks just fine.
Regards
I built the version 3.1
As Borys said the bias is rock solid. After 20 min since turn-on power bias is stabilising on around 98mA and for 3h is still 98mA. All the time.
I listen little time and I must said, that is rather retail or realistic sound, not "lovely" , "sweet" sound.
An externally hosted image should be here but it was not working when we last tested it.
As Borys said the bias is rock solid. After 20 min since turn-on power bias is stabilising on around 98mA and for 3h is still 98mA. All the time.
I listen little time and I must said, that is rather retail or realistic sound, not "lovely" , "sweet" sound.
Hi All!
I made my own lay-out based on VSSA BJT by Borys. I'm kind of liking the BJT version for the reason of parts availability. I have made the input pair to be 2SC2240/A970 and the CCS to be 2SC1845/A992. These types are very much available here in my place. My lay-out is not final, not till Borys (or somebody who has the skill) will post results of a stable VSSA BJT version. Sorry I do not have the skill to properly test this amp.
Best Regards!
I made my own lay-out based on VSSA BJT by Borys. I'm kind of liking the BJT version for the reason of parts availability. I have made the input pair to be 2SC2240/A970 and the CCS to be 2SC1845/A992. These types are very much available here in my place. My lay-out is not final, not till Borys (or somebody who has the skill) will post results of a stable VSSA BJT version. Sorry I do not have the skill to properly test this amp.
Best Regards!
Attachments
These could be an option for higher power version as Vceo rated at 120V and HFE BL rank at 300-700...
Marc
