up for a challenge? I need help finding a sub for a discontinued MOSFET

Thread Starter

loosecannon

Joined Aug 13, 2013
17
Hi all.

There is a MOSFET in a TO-218 package that is being used as an RF amplifier in two way radio applications.

I believe that it is just a re-labeled part, as the company that sells them is not a manufacturer.

This part has become unavailable from them, but i think that it is probably a much more commonly available part that was just re-labeled and re-purposed for use in an RF amplifier circuit.

here is the datasheet: http://www.ralphselectronics.com/ProductImages/SEMI-ERF7530.PDF

hopefully there is someone here who is adept at interpreting datasheets and can tell me what part the ERF7530 really is.

thanks in advance!
LC
 

wayneh

Joined Sep 9, 2010
16,399
The very minimum you need to specify a MOSFET is the rated voltage and current, 50V and 15A in this case. I wouldn't choose a replacement with specs lower than those.

If space is tight I'd want the same package. I've replaced MOSFETs using larger packages - bigger is better if you have room - but if you do that, be careful about lead size. Large leads may require reaming out the holes on the board. You can certainly do that but it can be hassle. An avoidable hassle.

RF is a mystery to me but this MOSFET was obviously specifically designed for the RF power application and that's what I'd look for in a replacement. If the replacement you consider is OK at 30MHz or higher, it should be fine. You certainly want a comparable power rating, although it may take some study to compare apples and oranges if the manufacturers are not consistent in how they define the various parameters.
 

Thread Starter

loosecannon

Joined Aug 13, 2013
17
yes, those are the parts in question, but as you can see they are fetching a premium price because they are not available anymore.

This company did this in the past with a part they called the ERF2030, and tried to charge 10 dollars a piece for them.
through much discussion, our forum gurus were able to determine that this was just an IRF520 mosfet that had been re-labeled.
Once the secret was out, even the manufacturers started using the IRF part instead. LOL

it seems now though that this new part has stumped our best and brightest, so i am reaching out to the engineering community for some help.
thanks to all for the interest!
 

Thread Starter

loosecannon

Joined Aug 13, 2013
17
The very minimum you need to specify a MOSFET is the rated voltage and current, 50V and 15A in this case. I wouldn't choose a replacement with specs lower than those.

If space is tight I'd want the same package. I've replaced MOSFETs using larger packages - bigger is better if you have room - but if you do that, be careful about lead size. Large leads may require reaming out the holes on the board. You can certainly do that but it can be hassle. An avoidable hassle.

RF is a mystery to me but this MOSFET was obviously specifically designed for the RF power application and that's what I'd look for in a replacement. If the replacement you consider is OK at 30MHz or higher, it should be fine. You certainly want a comparable power rating, although it may take some study to compare apples and oranges if the manufacturers are not consistent in how they define the various parameters.
thank you for the response.

because this company has done this in the past, by calling their part the "ERF2030" which turned out to be a plain old IRF520, we in our little hobby believe that this TO-218 mosfet is probably the same deal.

someone figured out how to use the gate capacitance to their advantage and make a mosfet work in an RF high freq. application.
I am sure that they did the same thing with the other larger part, and that most likely the original part that go re-labeled was not specifically intended for RF use.
 

Thread Starter

loosecannon

Joined Aug 13, 2013
17
here is a schematic of one product this mosfet is being used in: http://www.cbtricks.com/Amp/powerband/rfx_75/graphics/rfx75_schematic_rev4.pdf

this product is no longer available, and was never that great to begin with, but it should provide some insight into how this part is used.

I still cant help but think that there is a TO-218 package mosfet out there with different numbers on the front, but the exact same specs.
NTE has been doing this forever.
 

ian field

Joined Oct 27, 2012
6,539
Hi all.

There is a MOSFET in a TO-218 package that is being used as an RF amplifier in two way radio applications.

I believe that it is just a re-labeled part, as the company that sells them is not a manufacturer.

This part has become unavailable from them, but i think that it is probably a much more commonly available part that was just re-labeled and re-purposed for use in an RF amplifier circuit.

here is the datasheet: http://www.ralphselectronics.com/ProductImages/SEMI-ERF7530.PDF

hopefully there is someone here who is adept at interpreting datasheets and can tell me what part the ERF7530 really is.

thanks in advance!
LC
I have a sneaky suspicion that an IRF530 might do it - they're not exactly uncommon in radio amateur DIY rigs.

There are a lot of competing gate technologies so look for the 530 "base number" from a manufacturer boasting low gate capacitance.
 

ian field

Joined Oct 27, 2012
6,539
yes, those are the parts in question, but as you can see they are fetching a premium price because they are not available anymore.

This company did this in the past with a part they called the ERF2030, and tried to charge 10 dollars a piece for them.
through much discussion, our forum gurus were able to determine that this was just an IRF520 mosfet that had been re-labeled.
Once the secret was out, even the manufacturers started using the IRF part instead. LOL

it seems now though that this new part has stumped our best and brightest, so i am reaching out to the engineering community for some help.
thanks to all for the interest!
As I mentioned elsewhere - it has a faint niff of the IRF530 about it.

There are competing manufacturers boasting the lowest gate capacitance from their unique technology - pick the lowest.

Yours could be an isolated tab variant - having to use an insulating mounting kit will probably have a different drain to heat sink capacitance.
 
Top