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source pins together). That will not increase voltage rating. ItHey all;
If I connect the drain of one JFET to the drain of another (same device),
will it double the reverse gate drain voltage rating? So, if each device is
rated at 25v gate drain voltage, will it now be 50v?
Thanks
You're describing a parallel connection (assuming you also put the
No.Hey all;
If I connect the drain of one JFET to the drain of another (same device),
will it double the reverse gate drain voltage rating? So, if each device is
rated at 25v gate drain voltage, will it now be 50v?
Thanks
On Sat, 27 Mar 2004 10:58:48 -0500, "tempus fugit"
toccata@no.spam.ciaccess.com> wrote:
Hey all;
If I connect the drain of one JFET to the drain of another (same device),
will it double the reverse gate drain voltage rating? So, if each device
is
rated at 25v gate drain voltage, will it now be 50v?
Thanks
No.
John
Do the PIV rating increases when two diodes are placed in series?On Sat, 27 Mar 2004 10:58:48 -0500, "tempus fugit"
toccata@no.spam.ciaccess.com> wrote:
Hey all;
If I connect the drain of one JFET to the drain of another (same device),
will it double the reverse gate drain voltage rating? So, if each device is
rated at 25v gate drain voltage, will it now be 50v?
Thanks
No.
John
John Larkin <jjlarkin@highlandSNIPtechTHISnologyPLEASE.com> wrote in
message news:<2bcb605fe1ih4vrc87apmfpijm2904360k@4ax.com>...
On Sat, 27 Mar 2004 10:58:48 -0500, "tempus fugit"
toccata@no.spam.ciaccess.com> wrote:
Hey all;
If I connect the drain of one JFET to the drain of another (same
device),
will it double the reverse gate drain voltage rating? So, if each
device is
rated at 25v gate drain voltage, will it now be 50v?
Thanks
No.
John
Do the PIV rating increases when two diodes are placed in series?
Regards,
Animesh Maurya
Yes.John Larkin <jjlarkin@highlandSNIPtechTHISnologyPLEASE.com> wrote in message news:<2bcb605fe1ih4vrc87apmfpijm2904360k@4ax.com>...
On Sat, 27 Mar 2004 10:58:48 -0500, "tempus fugit"
toccata@no.spam.ciaccess.com> wrote:
Hey all;
If I connect the drain of one JFET to the drain of another (same device),
will it double the reverse gate drain voltage rating? So, if each device is
rated at 25v gate drain voltage, will it now be 50v?
Thanks
No.
John
Do the PIV rating increases when two diodes are placed in series?
Regards,
Animesh Maurya
and predictably with a voltage equalization networkDo the PIV rating increases when two diodes are placed in series?
Animesh Maurya
Yes.
John Larkin
That depends. Controlled-avalanche diodes (which don't have aDo the PIV rating increases when two diodes are placed in series?
Animesh Maurya
Yes.
John Larkin
and predictably with a voltage equalization network
http://images.google.com/images?&q=series-connected-diodes+powerdesigners
Your ASCII technique is better than many a guy's graphics.. D o
. |
. ,--------+
. | |
. R2 |--'
. | |
. +---->|--, Q2
. | |
. R1 |
. | |--'
. G | |
. o--| --->|--, Q1
. | |
. '--------+
. |
. S o
Win Hill
No, just insert mode in whatever text editor is handy.. D o
. |
. ,--------+
. | |
. R2 |--'
. | |
. +---->|--, Q2
. | |
. R1 |
. | |--'
. G | |
. o--| --->|--, Q1
. | |
. '--------+
. |
. S o
Win Hill
Your ASCII technique is better than many a guy's graphics.
Do you use more than a text editor?
tempus fugit wrote...
If I connect the drain of one JFET to the drain of another (same
device),
will it double the reverse gate drain voltage rating? So, if each device
is rated at 25v gate drain voltage, will it now be 50v?
It's not generally not the best solution to a problem, but there may
be times when it makes sense. It's necessary to establish the 2nd
JFET as an active voltage divider and to insure that the first JFET
controls the cascode pair. More or less like this:
. D o
. |
. ,--------+
. | |
. R2 |--'
. | |
. +---->|--, Q2
. | |
. R1 |
. | |--'
. G | |
. o--| --->|--, Q1
. | |
. '--------+
. |
. S o
Clearly R1 = R2 to split the drain voltage. They may also need to be
high-resistance values to insure the source current doesn't interfere
with the pair acting like a single higher-voltage JFET. But using a
high resistor value could mean slowing down Q2, which could be a problem.
So it's necessary to have a complete understanding of the circuit and to
apply the appropriate circuit measures to solve any remaining problems.
Thanks,
- Win
whill_at_picovolt-dot-com
Dual n-channel JFETs have always been expensive. Why would such aThe reason I'm asking is that I'm repairing a keyboard and the part that
failed is a DUAL nchannel JFET. Since these are pretty scarce, I figured
I might try a cheaper alternative, particularly since i'm not sure if
something else caused the original to fail, at least until I get it up
and running again.
and the FETs were there at the input of an op-amp to make a high-impedancetempus fugit wrote...
The reason I'm asking is that I'm repairing a keyboard and the part that
failed is a DUAL nchannel JFET. Since these are pretty scarce, I figured
I might try a cheaper alternative, particularly since i'm not sure if
something else caused the original to fail, at least until I get it up
and running again.
Dual n-channel JFETs have always been expensive. Why would such a
part be used in a keyboard? What kind of keyboard? What does this
have to do with your question about increasing the voltage rating?
Thanks,
- Win
whill_at_picovolt-dot-com
I wondered myself. Then I thought maybe it was an analog music keyboard,
Winfield Hill (Winfield_member@newsguy.com) writes:
tempus fugit wrote...
The reason I'm asking is that I'm repairing a keyboard and the part
that
failed is a DUAL nchannel JFET. Since these are pretty scarce, I
figured
I might try a cheaper alternative, particularly since i'm not sure if
something else caused the original to fail, at least until I get it up
and running again.
Dual n-channel JFETs have always been expensive. Why would such a
part be used in a keyboard? What kind of keyboard? What does this
have to do with your question about increasing the voltage rating?
Thanks,
- Win
whill_at_picovolt-dot-com
I wondered myself. Then I thought maybe it was an analog music keyboard,
and the FETs were there at the input of an op-amp to make a high-impedance
op-amp. Such a scheme was a fairly common scheme until FET-input op-amps
came along. You wanted a dual JFET so they were a matched pair.
If that's a wrong assumption, then of course it's worth looking at what
the dual JFET is there for. I find it hard to imagine a condition that
would set it up, but for all we know it could just be that the board
needed
two FETs, so they used a dual FET even if they aren't used together. That
would allow for a simple solution, two separate FETs.
Michael
would be to pull out the FETs and the op-amp, and replace the wholeYou hit the nail on the head Michael. It is in fact an old analog keyboard,
and the dual jfet is there in conjunction with a 1458 to make a high Z
opamp. I also wondered if it's the matched pair that is necessary, but from
your comments, it seems like it is. The drains are in fact wired together on
the board.
What function is this stage accomplishing? An obvious possibility
"Michael Black" <et472@FreeNet.Carleton.CA> wrote in message
news:c4c5bd$nct$1@freenet9.carleton.ca...
Winfield Hill (Winfield_member@newsguy.com) writes:
tempus fugit wrote...
The reason I'm asking is that I'm repairing a keyboard and the part
that
failed is a DUAL nchannel JFET. Since these are pretty scarce, I
figured
I might try a cheaper alternative, particularly since i'm not sure if
something else caused the original to fail, at least until I get it up
and running again.
Dual n-channel JFETs have always been expensive. Why would such a
part be used in a keyboard? What kind of keyboard? What does this
have to do with your question about increasing the voltage rating?
Thanks,
- Win
whill_at_picovolt-dot-com
I wondered myself. Then I thought maybe it was an analog music keyboard,
and the FETs were there at the input of an op-amp to make a high-impedance
op-amp. Such a scheme was a fairly common scheme until FET-input op-amps
came along. You wanted a dual JFET so they were a matched pair.
If that's a wrong assumption, then of course it's worth looking at what
the dual JFET is there for. I find it hard to imagine a condition that
would set it up, but for all we know it could just be that the board
needed
two FETs, so they used a dual FET even if they aren't used together. That
would allow for a simple solution, two separate FETs.
Michael
"tempus fugit" (toccata@no.spam.ciaccess.com) writes:
You hit the nail on the head Michael. It is in fact an old analog
keyboard,
and the dual jfet is there in conjunction with a 1458 to make a high Z
opamp. I also wondered if it's the matched pair that is necessary, but
from
your comments, it seems like it is. The drains are in fact wired
together on
the board.
What function is this stage accomplishing? An obvious possibility
would be to pull out the FETs and the op-amp, and replace the whole
thing with a JFET input op-amp. Whether or not that is feasible would
depend on the specific circuit, and of course whether you are simply
trying
to use the keyboard, or want to keep it authentic.
Michael
"Michael Black" <et472@FreeNet.Carleton.CA> wrote in message
news:c4c5bd$nct$1@freenet9.carleton.ca...
Winfield Hill (Winfield_member@newsguy.com) writes:
tempus fugit wrote...
The reason I'm asking is that I'm repairing a keyboard and the part
that
failed is a DUAL nchannel JFET. Since these are pretty scarce, I
figured
I might try a cheaper alternative, particularly since i'm not sure
if
something else caused the original to fail, at least until I get it
up
and running again.
Dual n-channel JFETs have always been expensive. Why would such a
part be used in a keyboard? What kind of keyboard? What does this
have to do with your question about increasing the voltage rating?
Thanks,
- Win
whill_at_picovolt-dot-com
I wondered myself. Then I thought maybe it was an analog music
keyboard,
and the FETs were there at the input of an op-amp to make a
high-impedance
op-amp. Such a scheme was a fairly common scheme until FET-input
op-amps
came along. You wanted a dual JFET so they were a matched pair.
If that's a wrong assumption, then of course it's worth looking at what
the dual JFET is there for. I find it hard to imagine a condition that
would set it up, but for all we know it could just be that the board
needed
two FETs, so they used a dual FET even if they aren't used together.
That
would allow for a simple solution, two separate FETs.
Michael