Ideal FET question

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Postby steve_qix » Thu Dec 21, 2006 7:35 pm

Best MOSFET --- From my prespective, having designed and built a lot of class E amplifiers, the best FET has the highest possible voltage rating with the lowest possible input capacitance. Also, this ideal MOSFET must be in a package that requires minimal mounting hardware.

AND IT MUST BE CHEAP !!!!!

So far the FQA11N90 is the best because it meets all of the above.

Someone mentioned PEP V/S Carrier power. All of my designs assume a PEP 9x the carrier. This is typical for 200% positive modulation. Even 150% will yield something like 6.25 x carrier. Then you have to allow for a safety factor, too !

Regards,

Steve
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Postby cableman » Wed Dec 27, 2006 9:31 am

Finally found today a importer who will sell me the FQA11N90 here local.
So no more searche for other fets,going to use the best now.

It is going to be appr 100W carrier to start with.
I want to make a fixed 50 ohm output,and a amidon T200-2 core in stead of a aircoil.

So what i like to know,for my matching simulation.
What would be the impedance after the outputtransformer,if i use 1 or 2 fets per bank?


And another guestion:
Do i have to use the same resistornetwork on the input of a DEIC420,on a IXDD414?

Greetings and a cool 2007!

Bert
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Postby steve_qix » Mon Jan 01, 2007 9:22 pm

cableman wrote:Finally found today a importer who will sell me the FQA11N90 here local.
So no more searche for other fets,going to use the best now.

It is going to be appr 100W carrier to start with.
I want to make a fixed 50 ohm output,and a amidon T200-2 core in stead of a aircoil.

So what i like to know,for my matching simulation.
What would be the impedance after the outputtransformer,if i use 1 or 2 fets per bank?


And another guestion:
Do i have to use the same resistornetwork on the input of a DEIC420,on a IXDD414?

Greetings and a cool 2007!

Bert


I'd have to think about the impedance question...however on using an IXDD414 for a driver - what are you driving it with? I have changed the VFO output to include an IXDD414 to drive whatever is the driver for the MOSFET gates - including an IXDD414 or a DEIC420. I have changed the resistive termination to be a 50 ohm resistor to ground or a 50 ohm resistor to +5. This will force the drive to be in one state or the other, and the IXDD414 driver at the VFO can drive this no problem. If you are using some other source of RF, I'd have to know what that is to answer the question differently.

Regards,

Steve
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Postby cableman » Tue Jan 02, 2007 3:57 am

Thanks for the reply Steve,

The drive is going to be 5V TTL.
The Cypress clock-oscillator(3,3V) buffered by a 74H14 schmitt-trigger(5V)
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