I'm building a circuit that calls for a dual monolithic
jfet. Can I use two discrete jfets that I have matched
for IDSS in the circuit? They are in TO92 plastic
cases, I can glue the two in contact with each other
so they end up at the same temperature.

On Mon, 09 Jan 2006 17:01:59 -0500, Ken Scharf
wrote:

I'm building a circuit that calls for a dual monolithic
jfet. Can I use two discrete jfets that I have matched
for IDSS in the circuit? They are in TO92 plastic
cases, I can glue the two in contact with each other
so they end up at the same temperature.

Yes, you can but the closer the match the better.
Two parts form the same lot/datecode with the same
IDSS should be ok.

I've done this with MPF102s (a wide tolerence part)
with good results in all but extremely critical designs.

Allison

Depends on the particular application, but this sounds reasonable. However,
rather than IDss, I'd shoot for what ever bias current they are operated at,
though IDss may work,
73, K,9.D;C'I


"Ken Scharf" wrote in message
. ..
I'm building a circuit that calls for a dual monolithic
jfet. Can I use two discrete jfets that I have matched
for IDSS in the circuit? They are in TO92 plastic
cases, I can glue the two in contact with each other
so they end up at the same temperature.

If you match both Idss and Vp, they'll have the same Gm at all currents
-- in theory.

Roy Lewallen, W7EL

Steve Nosko wrote:
Depends on the particular application, but this sounds reasonable. However,
rather than IDss, I'd shoot for what ever bias current they are operated at,
though IDss may work,
73, K,9.D;C'I


"Ken Scharf" wrote in message
. ..

I'm building a circuit that calls for a dual monolithic
jfet. Can I use two discrete jfets that I have matched
for IDSS in the circuit? They are in TO92 plastic
cases, I can glue the two in contact with each other
so they end up at the same temperature.

"Roy Lewallen" wrote in message
...
If you match both Idss and Vp, they'll have the same Gm at all currents --
in theory.

Roy Lewallen, W7EL

Steve Nosko wrote:
Depends on the particular application, but this sounds reasonable.
However,
rather than IDss, I'd shoot for what ever bias current they are operated
at,
though IDss may work,
73, K,9.D;C'I


"Ken Scharf" wrote in message
. ..

I'm building a circuit that calls for a dual monolithic
jfet. Can I use two discrete jfets that I have matched
for IDSS in the circuit? They are in TO92 plastic
cases, I can glue the two in contact with each other
so they end up at the same temperature.

i have u401 and e402 dual fets, new but unused.
any use to you?

martyn G0THY

"Martyn" wrote in message
...

"Roy Lewallen" wrote in message
...
If you match both Idss and Vp, they'll have the same Gm at all
currents -- in theory.

Roy Lewallen, W7EL

Steve Nosko wrote:
Depends on the particular application, but this sounds reasonable.
However,
rather than IDss, I'd shoot for what ever bias current they are operated
at,
though IDss may work,
73, K,9.D;C'I


"Ken Scharf" wrote in message
. ..

I'm building a circuit that calls for a dual monolithic
jfet. Can I use two discrete jfets that I have matched
for IDSS in the circuit? They are in TO92 plastic
cases, I can glue the two in contact with each other
so they end up at the same temperature.

i have u401 and e402 dual fets, new but unused.
any use to you?

martyn G0THY

or even Old, but unused. oops

Martyn wrote:
"Roy Lewallen" wrote in message
...

If you match both Idss and Vp, they'll have the same Gm at all currents --
in theory.

Roy Lewallen, W7EL

Steve Nosko wrote:

Depends on the particular application, but this sounds reasonable.
However,
rather than IDss, I'd shoot for what ever bias current they are operated
at,
though IDss may work,
73, K,9.D;C'I


"Ken Scharf" wrote in message
et...


I'm building a circuit that calls for a dual monolithic
jfet. Can I use two discrete jfets that I have matched
for IDSS in the circuit? They are in TO92 plastic
cases, I can glue the two in contact with each other
so they end up at the same temperature.

i have u401 and e402 dual fets, new but unused.

any use to you?

martyn G0THY


Thnaks for the offer.
The specs on the U401 would work out fine for my application.
What would you want for a pair of them?

Ken, WA2MZE

"wa2mze(spamless)" wrote in message
. ..
Martyn wrote:
"Roy Lewallen" wrote in message
...

If you match both Idss and Vp, they'll have the same Gm at all
currents --
in theory.

Roy Lewallen, W7EL

Steve Nosko wrote:

Depends on the particular application, but this sounds reasonable.
However,
rather than IDss, I'd shoot for what ever bias current they are operated
at,
though IDss may work,
73, K,9.D;C'I


"Ken Scharf" wrote in message
. net...


I'm building a circuit that calls for a dual monolithic
jfet. Can I use two discrete jfets that I have matched
for IDSS in the circuit? They are in TO92 plastic
cases, I can glue the two in contact with each other
so they end up at the same temperature.

i have u401 and e402 dual fets, new but unused.

any use to you?

martyn G0THY


Thnaks for the offer.
The specs on the U401 would work out fine for my application.
What would you want for a pair of them?

Ken, WA2MZE

been to QRZ, they are on the way to you.

martyn G0THY