What Dual Gate MOSFET for small signal RF Amplifier circuit in HF band... & where to buy?

Thread Starter

Fran3

Joined Mar 28, 2019
19
Looking at HF receiver schematics on line I see many use Dual Gate MOSFET's as the first amplifier stage... and also for the mixer... mixing the incoming RF signal with the local oscillator.

However all of the MOSFET's I've checked out seem to be out of production... and the ones I've found seem to be for switching and control applications... not small signal RF amplifiers for the 1.8MHz to 30 MHz band and/or rf mixers for down conversion to IF.

What manufacturers are still making Dual Gate MOSFETS... or just FET's for use in such circuits... small signal RF amplifier for 1.8MHz to 30MHz range.
Can you suggest a part number?
Where can I buy these parts? (other than eBay)

Thanks for any help.
 

Thread Starter

Fran3

Joined Mar 28, 2019
19
Hello,

There are many available.
Have a look for the BF960, BF980 , BF901, BF904 or BF909.
https://www.alldatasheet.com/view.jsp?Searchword=BF980

Bertus
As far as I can find all these parts are obsolute and DigiKey shows that status with zero inventory.
Also, I could not find them on the NXP Semiconductor website... aka the manufacturers website.
Any other suggestions would still be helpful for something that is still in production and available.
 

Thread Starter

Fran3

Joined Mar 28, 2019
19
Thanks Bertus... I will take a look at those links.

But all this makes me wonder why it seems so hard to find a dual gate MOSFET for small signal RF in the HF band that is still in active production.
I'm beginning think that for a new design that is expected to be in production for a number of years... maybe an alternate design approach would be more stable.
I've never been a big fan of using inventory remnants in a new product design... not to mention wanting at least one second manufacturing source.
Any ideas on what is going on in the dual-gate design and manufacturing world? Have most of the semi-conducor manufactures switch their capacity over to make different parts or what?
Thanks for any input on this as I've been out of the new design picture for a few years and have a lot of catching up to do.
 

Thread Starter

Fran3

Joined Mar 28, 2019
19
Could you be looking at leaded vs lead-free perhaps? I hit that snag when looking up ICs for a project.
Well, I didn't intentionally look for the MOSFET with leads but that is my preference. I could make the surface mount work but in this particular application one leads would be the first choice... that said, I'm striking out on dual gate MOSFET devices for use in small signal HF 1.8 to 30 MHz frequency range.
 

metermannd

Joined Oct 25, 2020
36
By leaded vs. lead-free, I was talking about the element.

Many parts produced for use with conventional tin / lead soldering processes have been superseded by parts produced in accordance with the RoHS initiative (Reduction of hazardous substances - i.e., discontinuing use of lead, cadmium, etc...), in some cases resulting in a part number or part number suffix change.
 

Thread Starter

Fran3

Joined Mar 28, 2019
19
If the parts are not soldered how are they attached to the PC board?
I've been out of tech design for quite a few years and am trying to catch up. Thanks.
 

Thread Starter

Fran3

Joined Mar 28, 2019
19
Ah Ha! Communication break down. My bad, as they say these days.
In your earlier comment... " Could you be looking at leaded vs lead-free perhaps? I "
I thought you earlier referring to components with no leads... aka SMT components...
But here... " Many parts produced for use with conventional tin / lead soldering processes have been superseded "
you were referring to, I assume, the pre-tinned pins/wires extending out of a transistor, dip, sip, or IC... correct?
Or what?
Again, I've been out of the loop for many years so pardon me while I catch up:)
 
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