Dual Gate Mosfets DATA and Information Page Earl VE3AB
www.earlandrews.com
www.earlandrews.com
BF981
I bought some of these in bulk ie lots of 20 or so.
They are much less in cost than the RCA 40673 discontinued dg mosfet.
Enterprising hams can perhaps adapt these to their circuits or solder fine transistor lead material to the axial
leads thus creating radial wire leads.
I'll take some pictures when I try this myself in the near future.
Even though it is gate protected with back to back diodes...I would use a ground strap or ground yourself
frequently when handling.
I bought some of these in bulk ie lots of 20 or so.
They are much less in cost than the RCA 40673 discontinued dg mosfet.
Enterprising hams can perhaps adapt these to their circuits or solder fine transistor lead material to the axial
leads thus creating radial wire leads.
I'll take some pictures when I try this myself in the near future.
Even though it is gate protected with back to back diodes...I would use a ground strap or ground yourself
frequently when handling.
BF981 PICTURED BELOW. -- COMMONLY AVAILABLE AT A
REASONABLE PRICE.
REASONABLE PRICE.
rca 40673 (nte (an aftermarket distributor) NTE222 (ecg 222)
At a fast glance at the specs, the drain current is
less than half for this bf981 than the 40673.
Perhaps the DC biasing voltages and currents might
have to be altered (resistors/dc voltages).
Iam a technician not engineer. For the low price of
these devices, I would be inclined (myself)to try it in
the circuit as a direct substitute for the 40673 and
see if it works.
I did this very thing with the FT301 radio I was
working on. I tried a substitute device and it worked
and (in fact) seemed to work as well or better than
the original dg mosfet.
I belong to a list QRP-L. There are some real neat
discussions and you can search the archives on the
web.
SOME OF THE POSTS ABOUT 40673 DG MOSFETS and
substitutes are in text at the bottom of this page.
less than half for this bf981 than the 40673.
Perhaps the DC biasing voltages and currents might
have to be altered (resistors/dc voltages).
Iam a technician not engineer. For the low price of
these devices, I would be inclined (myself)to try it in
the circuit as a direct substitute for the 40673 and
see if it works.
I did this very thing with the FT301 radio I was
working on. I tried a substitute device and it worked
and (in fact) seemed to work as well or better than
the original dg mosfet.
I belong to a list QRP-L. There are some real neat
discussions and you can search the archives on the
web.
SOME OF THE POSTS ABOUT 40673 DG MOSFETS and
substitutes are in text at the bottom of this page.
NTE/ECG are good aftermarket sources but can
be a bit pricey.
NTE has an on line CROSS REFERENCE TOOL
and you can download PDF files of the data
sheet.
One ham in NewFoundland that I chat with the
odd time paid about $20 for a dg mosfet
aftermarket device.
I can supply you at a much lower price.
I keep all my DUAL GATE MOSFETS in static
packaging and in a metal cabinet.
I don't have a great deal of stock of these items
but I can supply up to a few at a time if you need
to fix or build something.
be a bit pricey.
NTE has an on line CROSS REFERENCE TOOL
and you can download PDF files of the data
sheet.
One ham in NewFoundland that I chat with the
odd time paid about $20 for a dg mosfet
aftermarket device.
I can supply you at a much lower price.
I keep all my DUAL GATE MOSFETS in static
packaging and in a metal cabinet.
I don't have a great deal of stock of these items
but I can supply up to a few at a time if you need
to fix or build something.
BELOW IS SOME "IDEAS" PRESENTED BY PEOPLE ON VARIOUS FORUMS on the internet concerning substitutes for common dg
mosfets --- I HAVE NOT verified if these ideas are completely true or not but they are presented to tinkerers and hobbyists LIKE
HAM experimenters and circuit builders.
According to my 1975 MOSFET Circuits Guidebook the RCA 40673 is a "consumer-type" substitute for the RCA 3N187, not that the 3N187 is
any easier to find. It is an N-channel depletion-type MOSFET with diodes protecting the gate.
-----------------------
If you want to deal with surface mount components, and there is nothing wrong with doing that, there are several parts that will replace it, try
the BFR991, BFR994, and with some care watching the Vds, the BF998. The good news is that these are all less than a buck at Digikey.
------------------------------------------------
I am trying to complete a receiver project from the ARRL HB(1980's) and find
> myself in need of RCA 40673's. I see them listed on eBay at a price of $6+.
> Is there any one selling these at a more resonable price? I realize these
> have not been generally used in the last 10 years or more.
> Possibly some one can suggest an inexpensive replacement?
A BF981 or something like it should work. The package is different, though. (my note: this is the one I would try as a substitute myself
noted by me Earl Andrews VE3AB..note..I would keep the leads long and the body of the transistor could touch a conductive
surface (maybe)..keeping the leads long (not cutting them off short) would/could dissipate the heat.
---------------------------------------------------
NTE has a substitute NTE222. You may try some vendors who sell NTE
transistors. Another substitute is the 3N201. This may require some bias
adjustment, however, I have substituted these directly for a 40673
---------------------------------------------------
mosfets --- I HAVE NOT verified if these ideas are completely true or not but they are presented to tinkerers and hobbyists LIKE
HAM experimenters and circuit builders.
According to my 1975 MOSFET Circuits Guidebook the RCA 40673 is a "consumer-type" substitute for the RCA 3N187, not that the 3N187 is
any easier to find. It is an N-channel depletion-type MOSFET with diodes protecting the gate.
-----------------------
If you want to deal with surface mount components, and there is nothing wrong with doing that, there are several parts that will replace it, try
the BFR991, BFR994, and with some care watching the Vds, the BF998. The good news is that these are all less than a buck at Digikey.
------------------------------------------------
I am trying to complete a receiver project from the ARRL HB(1980's) and find
> myself in need of RCA 40673's. I see them listed on eBay at a price of $6+.
> Is there any one selling these at a more resonable price? I realize these
> have not been generally used in the last 10 years or more.
> Possibly some one can suggest an inexpensive replacement?
A BF981 or something like it should work. The package is different, though. (my note: this is the one I would try as a substitute myself
noted by me Earl Andrews VE3AB..note..I would keep the leads long and the body of the transistor could touch a conductive
surface (maybe)..keeping the leads long (not cutting them off short) would/could dissipate the heat.
---------------------------------------------------
NTE has a substitute NTE222. You may try some vendors who sell NTE
transistors. Another substitute is the 3N201. This may require some bias
adjustment, however, I have substituted these directly for a 40673
---------------------------------------------------
SUBSTITUTES FOR THE VERY POPULAR RCA 40673 Dual Gate
Mosfet. Discussion from QRP-L the Low Power QRP and technical
group I subscribe to. As one fellow says : ARRL 1980s Handbook
had a few receiver projects and other radio projects that used dual
gate mosfets such as the RCA 40673.
Whatever subsitute you try: try to get the one with diodes
protecting the gate. My Ten TEc Argonaut 505,509 and 515 use a
dual gate mosfet in the RF amplifier stage. Back to back diodes on
the antenna line to the receive RF amp (DG Mosfet) will aid to
protect against static spikes which can damage these high
impedance devices. Make sure you ground yourself before and
during handling. Store them in a static safe storage bag with
antistatic foam on the leads or a wire shorting out the leads.
Mosfet. Discussion from QRP-L the Low Power QRP and technical
group I subscribe to. As one fellow says : ARRL 1980s Handbook
had a few receiver projects and other radio projects that used dual
gate mosfets such as the RCA 40673.
Whatever subsitute you try: try to get the one with diodes
protecting the gate. My Ten TEc Argonaut 505,509 and 515 use a
dual gate mosfet in the RF amplifier stage. Back to back diodes on
the antenna line to the receive RF amp (DG Mosfet) will aid to
protect against static spikes which can damage these high
impedance devices. Make sure you ground yourself before and
during handling. Store them in a static safe storage bag with
antistatic foam on the leads or a wire shorting out the leads.
40673 substitutes listed at the bottom of the page.
These "house numbered" dual gate mosfets were bought by
me back in around the year 2000 or so from a fellow on QRP-L
(the technical and qrp list I belong to).
I bought them way back when and our dollar was only worth
about 65 cents or 70 cents to the american dollar.
I can spare a few for $1.75 each. I think they are similar to
3n211 (I can look it up).
I used one by forming the leads and it worked quite well in
my FT301 replacing a dual gate mosfet in the rcvr front end. I
also used them in a converter that had a couple of damaged
dg mosfets. Seemed to work ok but I need to evaluate the
circuit under real world conditions.
I CROSS REFERENCED THE MPF 131 TO BF 981,3SK49, MFE131
(electrically quite similar).
ID LIKE TO BUY MORE OF THIS KIND
OF STUFF IF ANY ONE HAS ANY TO
SELL.
me back in around the year 2000 or so from a fellow on QRP-L
(the technical and qrp list I belong to).
I bought them way back when and our dollar was only worth
about 65 cents or 70 cents to the american dollar.
I can spare a few for $1.75 each. I think they are similar to
3n211 (I can look it up).
I used one by forming the leads and it worked quite well in
my FT301 replacing a dual gate mosfet in the rcvr front end. I
also used them in a converter that had a couple of damaged
dg mosfets. Seemed to work ok but I need to evaluate the
circuit under real world conditions.
I CROSS REFERENCED THE MPF 131 TO BF 981,3SK49, MFE131
(electrically quite similar).
ID LIKE TO BUY MORE OF THIS KIND
OF STUFF IF ANY ONE HAS ANY TO
SELL.
With these house numbered Dual Gate Mosfets, the pin out is a similar
layout to the metal can package dg mosfets and with a bit of lead forming
they can be used in place of the radial lead transistors. I did this with my
FT301 on the RF board and the circuit worked as well or better with this
substitute.
layout to the metal can package dg mosfets and with a bit of lead forming
they can be used in place of the radial lead transistors. I did this with my
FT301 on the RF board and the circuit worked as well or better with this
substitute.
To the left (pictured) the little pin out sheet that
came with these DG MOSFETS.
For $1.75 each they are inexpensive and seem
to work. I used them in a vhf converter that I
repaired and they worked ok there as well.
DIODE PROTECTED GATES ON THESE ONES AS
WELL.
HANDLE WITH CARE THOUGH..I WOULD GROUND
MYSELF BEFORE AND DURING HANDLING UNTIL
THEY ARE SOLDERED INTO THE CIRCUIT.
ESD ELECTRO STATIC SENSITIVE DEVICE
MOSFETS ARE PRONE TO ESD DAMAGE.
came with these DG MOSFETS.
For $1.75 each they are inexpensive and seem
to work. I used them in a vhf converter that I
repaired and they worked ok there as well.
DIODE PROTECTED GATES ON THESE ONES AS
WELL.
HANDLE WITH CARE THOUGH..I WOULD GROUND
MYSELF BEFORE AND DURING HANDLING UNTIL
THEY ARE SOLDERED INTO THE CIRCUIT.
ESD ELECTRO STATIC SENSITIVE DEVICE
MOSFETS ARE PRONE TO ESD DAMAGE.
I can supply a few of these DG MOSFETS that are similar to MPF 131s. See data
sheet pin out and specs on this page.
sheet pin out and specs on this page.
| http://www.datasheetarchive .com/ is where I get most of my data sheets and cross references-- it is great but I could not find the RCA 40673 listed there. I used the NTE semiconductor web site to find info and pdf file for this one. |
What we have here is the
underside of the circuit board and
a group of spare dual gate mosfets.
The dual gate mosfets are some in
house part number used by some
company but are (supposedly)
similar to type 3n201 dg mosfets.
REPLACING THE METAL CAN PACK
DG MOSFETS (2 OF THEM-- with
these economical plastic case dg
fets).
When mounted on the top
(component side) of the circuit
board; the pin layout does match
the pattern layout but the pins
themselves are too thick to go
through the holes in the circuit
board. (and they would likely have
to be formed to the physical layout
dimensions).
As a work around solution; I
flipped the leads upside down with
a pair of pliers and clipped them
and formed the leads and mounted
them upside down on the bottom
of the circuit board.
This is "OK" for amateur use.
Commercial vendors and
manufacturers would not do this
unless they could not avoid it.
underside of the circuit board and
a group of spare dual gate mosfets.
The dual gate mosfets are some in
house part number used by some
company but are (supposedly)
similar to type 3n201 dg mosfets.
REPLACING THE METAL CAN PACK
DG MOSFETS (2 OF THEM-- with
these economical plastic case dg
fets).
When mounted on the top
(component side) of the circuit
board; the pin layout does match
the pattern layout but the pins
themselves are too thick to go
through the holes in the circuit
board. (and they would likely have
to be formed to the physical layout
dimensions).
As a work around solution; I
flipped the leads upside down with
a pair of pliers and clipped them
and formed the leads and mounted
them upside down on the bottom
of the circuit board.
This is "OK" for amateur use.
Commercial vendors and
manufacturers would not do this
unless they could not avoid it.
Where I used to work for 18 years (with Military and ex Military Technicians and
supply people) I was sternly told that "work around solutions" were not the way to
do things. --- NOW that I am on my own and this is 'AMATEUR' equipment that does
not see any g-forces or does not have to withstand blasts or vibrations or
stresses of that nature.. work around solutions that make sense and save money
are the order of the day.
This is an 2 meter receive converter than ouputs on 27 mhz! A bit of a rare item.
Picked it up at a flea market for $2 w/manual. Both DG Mosfets needed to be
replaced. The converter now works. Not sure if it is low noise and good sensitivity
or not. I have not gotten around to comparision tests yet.
Up here in northern ontario, 2 meter ssb activity is not that common and I dont
have a good horizontal beam.
supply people) I was sternly told that "work around solutions" were not the way to
do things. --- NOW that I am on my own and this is 'AMATEUR' equipment that does
not see any g-forces or does not have to withstand blasts or vibrations or
stresses of that nature.. work around solutions that make sense and save money
are the order of the day.
This is an 2 meter receive converter than ouputs on 27 mhz! A bit of a rare item.
Picked it up at a flea market for $2 w/manual. Both DG Mosfets needed to be
replaced. The converter now works. Not sure if it is low noise and good sensitivity
or not. I have not gotten around to comparision tests yet.
Up here in northern ontario, 2 meter ssb activity is not that common and I dont
have a good horizontal beam.
| 2 dual gate mosfets replaced on the opposite side of the circuit board from the component side. I formed the leads and the chip is actually upside down on the circuit board. Work around solution that works! --- The converter now works!! This could work as well for the |
| Navigation Link to www.hamelectronicsmagazine.com/qrpparts |
| MY LIST OF AVAILABLE PARTS (Dual Gate MOSFETS) RCA40673 (I do have a few available) these are discontinued parts (discontinued in the 1980s). Best sources for quantity orders might be ebay, Scotts Radio parts or maybe Dans Small parts may still sell them. Dan is on vacation till February. BF981...I have about 30 available..see pic opposite. 3N211 I have a few I can spare..these FETs are favourite replacements in front ends of older radios. MPF131 style ...House numbered. I can spare some of these. I adapted the leads to a transistor socket in my FT301 front end and this dg mosfet performed a bit better than the original (or so it seemed to me). You can mount them upside down on a circuit board and solder them in. Ive done this too as a "fix" ...at $2 each they are an inexpensive alternative. **see picture near bottom of page on how I soldered them on a circuit board (on the bottom of circuit board rather than on top (component side) OTHER DG MOSFETS including surface mount small ones. I have numerous different varieties and I can check my stocks to see what I can spare and how much. Just shoot off an email to me ve3ab@rac.ca or earlinclayton@yahoo.com and I can help you out with small amounts. |
| BF981 extracts from DATA sheets. Full data sheet available: datasheetarchive.com |
NAVIGATION LINK to
www.hamelectronicsmagazine.com < a free on line ham radio
magazine by Earl Andrews VE3AB> 73 Earl VE3AB
LINK HERE TO GO TO THE HOME PAGE
www.hamelectronicsmagazine.com < a free on line ham radio
magazine by Earl Andrews VE3AB> 73 Earl VE3AB
LINK HERE TO GO TO THE HOME PAGE