How to choose a MOSFET for HF ????

[bobytronic]

RF MOSFET prices start at about $35 each !!!

I know that it's possible to use low cost power MOSFET like IRF or others ... but how choose this MOSFET (which parameters are essential for the HF ...)
Have you got some reference for an application at 5Mhz ?

Thanks...

 

[mr_ghz]

Hi bobytronic

What is your application? Do you need high power? Do you want to use your FET for digital or analog application?

Bye

 

[bobytronic]

Hi MisteR_Ghz!

I want to design an HF power amplifier:

BP: 5Mhz
POwer : about 60W

 

[MoonShine]

Hi,

In choosing an HPA for HF one must know the app; is it digital modulation requiring very high linearity and thus must back off 7-10dB from P1dB(like CDMA)? Or is it like EDGE requiring less backoff? Or perhaps it's RADAR? The app makes all the difference in how to design. BTW, I noticed Motorola now has a 100W CW device with push-pull topology in a plastic package.
That's my 2 cents worth...

Regards,
MoonShine

 

[bobytronic]

Hi,

This is an universal HPA for a large gamme of piezoelectric Load (Fosc between 1Mhz and 5Mhz, Zin = 50ohms at Fosc)
So, High linearity, High voltage, and High frequency (

==> 120V AC max, Gain >10dB, about 60W output ...

Regard

 

[flatulent]

rf transistors

Transistors designed for RF will take a wide range of load SWR values. The ones for other uses will burn up under these conditions.

 

[MoonShine]

Hi bobytronic,

I see; your looking for an RF switch; I'm working with RF 2GHz LDMOS. In that case, the Ron and the peak current capability and switching speed/power dissipation become important parameters. Thus, you're looking for a device that can handle the peak current and power dissipation and maintain the rise/fall time requirements.

My extra 2 cents worth..
Regards,
MoonShine