2stageEF high performance class AB power amp / 200W8R / 400W4R

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de Ocampo

de Ocampo

Member
Joined 2010
astx said:
You need those switches because VPSRR as a 1V sinus source is added between 50V power source and V+ from amplifier.
Input needs to be grounded during this test.

BR, Toni
Click to expand...

Sir Toni,

Connecting the input to ground I get a blank plot.
I tried switching to different functions at Voltage source (input) i.e. none, Pulse, Sine no response but if I put 1 at the AC amplitude, I get a reading. A little different from my other post, Is this valid?
Input voltage source is set to none. AC amplitude = 1.


Sa muli,
Albert
 

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astx

astx

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Joined 2011
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SA2015: using vertical mosfets IXTH80N20L and IXTH48P20P - SOA

AndrewT said:
...
My "rule for limiters" is:
All valid output signals must pass to all valid loadings.
...
Click to expand...

In post 2155 I showed a dual slope limiter which is designed to protect the amplifier in a worst case condition. The SOA limiter curve are designed to not violate the Tc 75 degree points. Short back EMF pulses are viewable and (hopefully) also within SOA limits. If I lower the bias voltage to fullfill your above needs of about 300mV the SOA limits are clearly and heavily violated. You only have the decision: lowest THD or good SOA protection.
You only can get lowest THD and good SOA protection if you add many many output pairs and oversize your amplifiers power limits.

BR, Toni
 
A

AndrewT

R.I.P.
Joined 2004
astx said:
In post 2155 I showed a dual slope limiter which is designed to protect the amplifier in a worst case condition. The SOA limiter curve are designed to not violate the Tc 75 degree points. Short back EMF pulses are viewable and (hopefully) also within SOA limits. If I lower the bias voltage to fullfill your above needs of about 300mV the SOA limits are clearly and heavily violated. You only have the decision: lowest THD or good SOA protection.
You only can get lowest THD and good SOA protection if you add many many output pairs and oversize your amplifiers power limits.

BR, Toni
Click to expand...
I remember your post2155, but I could not understand what the plots were trying to show.
 
T

thimios

Member
Joined 2009
astx said:
Dear Timios,

you may need a heatspreader. Operating the amplifier modules at about 450mA total bias dissipates 38W per side.
The modu heatsinks have 0.5 K/W for your 200x40x120mm sized heatsink parts. So the temperature rise above ambient will be minimum 19 degree. If you don't like up to 60 degree hot heatsinks in summer you can ask a local supplier for 2 pieces 200x80x6mm aluminium parts to build your own heatspreader.
(Will have a look into bin if I can find some suitable parts ... will send you an email soon.)

BR, Toni
Click to expand...
Good news!
I found this 200mmx80mm thickness 10mm.
 
astx

astx

Member
Joined 2011
Paid Member
Dave Zan said:
...
As you wish:) Which ones do you want?
...
Click to expand...

Thanks! If I would have a wish free for christmas ... ;)

  • 2SC3902T and 2SA1507T (onsemi; obsolete, but have tons of it)
  • 2SC4027T-H, 2SA1552T-H (onsemi; in production; datasheet values look extremely similar to 2SC3902/2SA1507; maybe SMD variants of them)
BR, Toni

P.S.: It's so sad that so many good transistors are no more in production.:RIP:
P.P.S.: The good news: I have most of the old parts on stock for future projects :)
 
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D

Dave Zan

Member
Joined 2010
astx said:
Thanks! If I would have a wish free for christmas ... ;)
  • 2SC3902T and 2SA1507T (onsemi; obsolete, but have tons of it)
  • 2SC4027T-H, 2SA1552T-H (onsemi; in production; datasheet values look extremely similar to 2SC3902/2SA1507; maybe SMD variants of them)
Click to expand...

If I make it back to Austria one day then you can buy me a drink;)
The 2SA1552/2SC4027 look OK, a few little kinks on the datasheet that I probably can't reproduce, maybe not real anyway.
I will play around with it, I expect that if you did a few of these then it would be possible to look at the datasheet and just write a model immediately, without conscious calculation.

Best wishes
David
 
astx

astx

Member
Joined 2011
Paid Member
Dave Zan said:
If I make it back to Austria one day then you can buy me a drink;)
The 2SA1552/2SC4027 look OK, a few little kinks on the datasheet that I probably can't reproduce, maybe not real anyway.
I will play around with it, I expect that if you did a few of these then it would be possible to look at the datasheet and just write a model immediately, without conscious calculation.

Best wishes
David
Click to expand...

Dear Dave,

you will be welcome at any time here in Austria! :)
Many thanks in advance!
If you need I could scan some pieces from different lots using my DCA77 pro.

BR, Toni
 
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