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Parallel mosfets




 
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Author Topic: Parallel mosfets  (Read 1337 times)
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VE3LYX
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« on: September 17, 2018, 11:28:49 AM »

This may be a dumb question but         so adding mosfets in parallel adds the ability to switch higher currents without fet damage but other then a slight drop in resistance does not add power as would happen when amplifying rathr then switching?
Don
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Don VE3LYX<br />Eng, DE & petite Francais
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« Reply #1 on: September 17, 2018, 12:46:29 PM »

If you can switch twice the current, you have twice the power, but the load resistance should be 2 timers lower. When you don't lower the load resistance, the FET's swich half the current as before and the resistive ON losses are less, but hardly noticable
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VE3LYX
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« Reply #2 on: September 17, 2018, 02:30:27 PM »

So that would be a yes? The fets are working half as hard if everything else remains the same.
So..how do you change the load resistance in practical terms if you want to..make it grunt. 1/2 the turns on the output transformer primary or?
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Don VE3LYX<br />Eng, DE & petite Francais
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« Reply #3 on: September 17, 2018, 05:58:54 PM »

So that would be a yes? The fets are working half as hard if everything else remains the same.
So..how do you change the load resistance in practical terms if you want to..make it grunt. 1/2 the turns on the output transformer primary or?

Don, Power is square law so reducing the primary by half or doubling the secondary would double the voltage and with the same load would also double the current giving four times the power.  So change the turns by root 2 or .707 less primary or 1.414 more secondary to double the power.

73s  Nigel
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VE3LYX
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« Reply #4 on: September 18, 2018, 07:45:30 AM »

Tnx. I am slowly beginning to comprehend this. I have a lash up.working but not yet comfortable. Driving was my obstacle but I got it working. I also suffer from toroiditess. Hosever there is hope.
Don
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Don VE3LYX<br />Eng, DE & petite Francais
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« Reply #5 on: September 18, 2018, 08:43:22 AM »

Tnx. I amslowly beginni g tocomprehend this. I have a lash up.working but not yet comfortable. Driving was my obstacle but I got ut worki g. I also suffer from toroiditess. Hosever there is hope.
Don
OK Don good fun stuff.  Good drivers are as important as good FETs.  I have a bunch of IXDD614s in both TO220 and DIP8 format that you can have to play with as I will never be using them. Not the best drivers in the world but they will work. You and Linda come over for coffee or I can mail them.

73s  Nigel
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VE3LYX
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« Reply #6 on: September 18, 2018, 10:16:30 AM »

We will stop on.our next Kingston adventure. Ill double check before we show up.
The other morning when you were on talking with the group.on.3885 I had a portable on here. I set it on  the floor and Radio was over checking it out. I think she recognized the voice.
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Don VE3LYX<br />Eng, DE & petite Francais
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