John said:Pulldown nfet, directly driven from the input. Pullup pfet, ac coupled
(that should be ok here, with low duty cycle). Pfet drive is just a
cap, a zener s-g, and a resistor g-gnd. OK, maybe add a resistor in
the pfet drain for powerup shoot-thru and short-circuit protection.
For one more part, you can dc-couple the whole thing.
You could almost do it with one spdt opto-solid-state relay, but
they're a tad slow.
John
I DID see other circuits in the thread, but I did not have time to
look and play with them. I had to ship the project last Friday and
did not have time to play around. But I assure you I will eventually
examine all replies for their technical merits.
As for my maturity, you may be right. But if one were to compare
your rant and this reply, I don't think you would win the maturity
prize. But I have sometimes observed that maturty and technical
ability have little to do with each other.
LOL- that's all adding up too. For a minute there, I thought you were
thinking about that Maxim isolated RS-232 drive with 50V withstanding
voltage, but their drive power is so weak, they're unusable.
Seems to me that 5 or 6 parts is better than 21.
I read in sci.electronics.design that John Larkin
Are you selling parts or buying, though?
John said:Pulldown nfet, directly driven from the input. Pullup pfet, ac coupled
(that should be ok here, with low duty cycle). Pfet drive is just a
cap, a zener s-g, and a resistor g-gnd. OK, maybe add a resistor in
the pfet drain for powerup shoot-thru and short-circuit protection.
For one more part, you can dc-couple the whole thing.
You could almost do it with one spdt opto-solid-state relay, but
they're a tad slow.
John said:Pulldown nfet, directly driven from the input. Pullup pfet, ac coupled
(that should be ok here, with low duty cycle). Pfet drive is just a
cap, a zener s-g, and a resistor g-gnd. OK, maybe add a resistor in
the pfet drain for powerup shoot-thru and short-circuit protection.
For one more part, you can dc-couple the whole thing.
You could almost do it with one spdt opto-solid-state relay, but
they're a tad slow.
Are you describing this?
View in a fixed-width font such as Courier.
. V+
. |
. +------+
. | |
. z |
. a |
. + | ||-
. +---||----+---||>
. | | ||-
. | [Rb] |
. | | [Rsc]
. | | |
. | --- +------>
. | /// |
. | ||-
. CMOS IN>----+-------------||<
. ||-
. |
. |
. |
. ---
. ///
.
.
.
. V+
. |
. +------+
. | |
. r |
. | |
. | ||-
. +---------+---||>
. | ||-
. c |
. vcc--b [Rsc]
. e |
. | +------>
. r |
. | ||-
. CMOS IN>----+-------------||<
. ||-
. |
. |
. |
. ---
. ///
.
John said:John Larkin wrote:
Pulldown nfet, directly driven from the input. Pullup pfet, ac coupled
(that should be ok here, with low duty cycle). Pfet drive is just a
cap, a zener s-g, and a resistor g-gnd. OK, maybe add a resistor in
the pfet drain for powerup shoot-thru and short-circuit protection.
For one more part, you can dc-couple the whole thing.
You could almost do it with one spdt opto-solid-state relay, but
they're a tad slow.
Are you describing this?
View in a fixed-width font such as Courier.
. V+
. |
. +------+
. | |
. z |
. a |
. + | ||-
. +---||----+---||>
. | | ||-
. | [Rb] |
. | | [Rsc]
. | | |
. | --- +------>
. | /// |
. | ||-
. CMOS IN>----+-------------||<
. ||-
. |
. |
. |
. ---
. ///
.
.
.
Right. Drains to the output.
Pretty obviously you don't want a sustained high on the input. If
that's a concern, you can use a common-base transistor to dc couple
things...
. V+
. |
. +------+
. | |
. r |
. | |
. | ||-
. +---------+---||>
. | ||-
. c |
. vcc--b [Rsc]
. e |
. | +------>
. r |
. | ||-
. CMOS IN>----+-------------||<
. ||-
. |
. |
. |
. ---
. ///
.
which is actually nicer, but a bit slower. Still 6 parts including the
[Rsc] thingie.
John
John said:John Larkin wrote:
Pulldown nfet, directly driven from the input. Pullup pfet, ac coupled
(that should be ok here, with low duty cycle). Pfet drive is just a
cap, a zener s-g, and a resistor g-gnd. OK, maybe add a resistor in
the pfet drain for powerup shoot-thru and short-circuit protection.
For one more part, you can dc-couple the whole thing.
You could almost do it with one spdt opto-solid-state relay, but
they're a tad slow.
Are you describing this?
View in a fixed-width font such as Courier.
. V+
. |
. +------+
. | |
. z |
. a |
. + | ||-
. +---||----+---||>
. | | ||-
. | [Rb] |
. | | [Rsc]
. | | |
. | --- +------>
. | /// |
. | ||-
. CMOS IN>----+-------------||<
. ||-
. |
. |
. |
. ---
. ///
.
.
.
Right. Drains to the output.
Pretty obviously you don't want a sustained high on the input. If
that's a concern, you can use a common-base transistor to dc couple
things...
. V+
. |
. +------+
. | |
. r |
. | |
. | ||-
. +---------+---||>
. | ||-
. c |
. vcc--b [Rsc]
. e |
. | +------>
. r |
. | ||-
. CMOS IN>----+-------------||<
. ||-
. |
. |
. |
. ---
. ///
.
which is actually nicer, but a bit slower. Still 6 parts including the
[Rsc] thingie.
John
But the requirement was to clamp the low going output at 6V down from
Vcc which was in the range 24-48 volts.
John said:John said:John Larkin wrote:
Pulldown nfet, directly driven from the input. Pullup pfet, ac coupled
(that should be ok here, with low duty cycle). Pfet drive is just a
cap, a zener s-g, and a resistor g-gnd. OK, maybe add a resistor in
the pfet drain for powerup shoot-thru and short-circuit protection.
For one more part, you can dc-couple the whole thing.
You could almost do it with one spdt opto-solid-state relay, but
they're a tad slow.
Are you describing this?
View in a fixed-width font such as Courier.
. V+
. |
. +------+
. | |
. z |
. a |
. + | ||-
. +---||----+---||>
. | | ||-
. | [Rb] |
. | | [Rsc]
. | | |
. | --- +------>
. | /// |
. | ||-
. CMOS IN>----+-------------||<
. ||-
. |
. |
. |
. ---
. ///
.
.
.
Right. Drains to the output.
Pretty obviously you don't want a sustained high on the input. If
that's a concern, you can use a common-base transistor to dc couple
things...
. V+
. |
. +------+
. | |
. r |
. | |
. | ||-
. +---------+---||>
. | ||-
. c |
. vcc--b [Rsc]
. e |
. | +------>
. r |
. | ||-
. CMOS IN>----+-------------||<
. ||-
. |
. |
. |
. ---
. ///
.
which is actually nicer, but a bit slower. Still 6 parts including the
[Rsc] thingie.
John
But the requirement was to clamp the low going output at 6V down from
Vcc which was in the range 24-48 volts.
Was it? That's silly. Why would anybody want to do that?
That would take 5 parts, too.
John
John said:John Larkin wrote:
John Larkin wrote:
Pulldown nfet, directly driven from the input. Pullup pfet, ac coupled
(that should be ok here, with low duty cycle). Pfet drive is just a
cap, a zener s-g, and a resistor g-gnd. OK, maybe add a resistor in
the pfet drain for powerup shoot-thru and short-circuit protection.
For one more part, you can dc-couple the whole thing.
You could almost do it with one spdt opto-solid-state relay, but
they're a tad slow.
Are you describing this?
View in a fixed-width font such as Courier.
. V+
. |
. +------+
. | |
. z |
. a |
. + | ||-
. +---||----+---||>
. | | ||-
. | [Rb] |
. | | [Rsc]
. | | |
. | --- +------>
. | /// |
. | ||-
. CMOS IN>----+-------------||<
. ||-
. |
. |
. |
. ---
. ///
.
.
.
Right. Drains to the output.
Pretty obviously you don't want a sustained high on the input. If
that's a concern, you can use a common-base transistor to dc couple
things...
. V+
. |
. +------+
. | |
. r |
. | |
. | ||-
. +---------+---||>
. | ||-
. c |
. vcc--b [Rsc]
. e |
. | +------>
. r |
. | ||-
. CMOS IN>----+-------------||<
. ||-
. |
. |
. |
. ---
. ///
.
which is actually nicer, but a bit slower. Still 6 parts including the
[Rsc] thingie.
John
But the requirement was to clamp the low going output at 6V down from
Vcc which was in the range 24-48 volts.
Was it? That's silly. Why would anybody want to do that?
That would take 5 parts, too.
John
Well- where do you put them?
John said:John said:John Larkin wrote:
John Larkin wrote:
Pulldown nfet, directly driven from the input. Pullup pfet, ac coupled
(that should be ok here, with low duty cycle). Pfet drive is just a
cap, a zener s-g, and a resistor g-gnd. OK, maybe add a resistor in
the pfet drain for powerup shoot-thru and short-circuit protection.
For one more part, you can dc-couple the whole thing.
You could almost do it with one spdt opto-solid-state relay, but
they're a tad slow.
Are you describing this?
View in a fixed-width font such as Courier.
. V+
. |
. +------+
. | |
. z |
. a |
. + | ||-
. +---||----+---||>
. | | ||-
. | [Rb] |
. | | [Rsc]
. | | |
. | --- +------>
. | /// |
. | ||-
. CMOS IN>----+-------------||<
. ||-
. |
. |
. |
. ---
. ///
.
.
.
Right. Drains to the output.
Pretty obviously you don't want a sustained high on the input. If
that's a concern, you can use a common-base transistor to dc couple
things...
. V+
. |
. +------+
. | |
. r |
. | |
. | ||-
. +---------+---||>
. | ||-
. c |
. vcc--b [Rsc]
. e |
. | +------>
. r |
. | ||-
. CMOS IN>----+-------------||<
. ||-
. |
. |
. |
. ---
. ///
.
which is actually nicer, but a bit slower. Still 6 parts including the
[Rsc] thingie.
John
But the requirement was to clamp the low going output at 6V down from
Vcc which was in the range 24-48 volts.
Was it? That's silly. Why would anybody want to do that?
That would take 5 parts, too.
John
Well- where do you put them?
Ain't it obvious?
John
John said:John Larkin wrote:
John Larkin wrote:
John Larkin wrote:
Pulldown nfet, directly driven from the input. Pullup pfet, ac coupled
(that should be ok here, with low duty cycle). Pfet drive is just a
cap, a zener s-g, and a resistor g-gnd. OK, maybe add a resistor in
the pfet drain for powerup shoot-thru and short-circuit protection.
For one more part, you can dc-couple the whole thing.
You could almost do it with one spdt opto-solid-state relay, but
they're a tad slow.
Are you describing this?
View in a fixed-width font such as Courier.
. V+
. |
. +------+
. | |
. z |
. a |
. + | ||-
. +---||----+---||>
. | | ||-
. | [Rb] |
. | | [Rsc]
. | | |
. | --- +------>
. | /// |
. | ||-
. CMOS IN>----+-------------||<
. ||-
. |
. |
. |
. ---
. ///
.
.
.
Right. Drains to the output.
Pretty obviously you don't want a sustained high on the input. If
that's a concern, you can use a common-base transistor to dc couple
things...
. V+
. |
. +------+
. | |
. r |
. | |
. | ||-
. +---------+---||>
. | ||-
. c |
. vcc--b [Rsc]
. e |
. | +------>
. r |
. | ||-
. CMOS IN>----+-------------||<
. ||-
. |
. |
. |
. ---
. ///
.
which is actually nicer, but a bit slower. Still 6 parts including the
[Rsc] thingie.
John
But the requirement was to clamp the low going output at 6V down from
Vcc which was in the range 24-48 volts.
Was it? That's silly. Why would anybody want to do that?
That would take 5 parts, too.
John
Well- where do you put them?
Ain't it obvious?
John
Stop screwing around and describe the circuit- unless it's proprietary
or something...you could be talking about any number of circuits.
[snip]Stop screwing around and describe the circuit- unless it's proprietary
or something...you could be talking about any number of circuits.
There's not a whole lot of ways to arrange 5 parts.
John
[snip]Well- where do you put them?
Ain't it obvious?
John
Stop screwing around and describe the circuit- unless it's proprietary
or something...you could be talking about any number of circuits.
There's not a whole lot of ways to arrange 5 parts.
John
Come on John, show us, or we'll conclude you're BS-ing ;-)
...Jim Thompson
Are you and Fred telling me you can't figure out how do
this with 5 parts? How disappointing.
John Larkin wrote...
I haven't been following. Is this a circuit for making a
+12V / -5V, 0.25A-capable gate-drive pulse from a wimpy
TTL logic signal? I can see doing it crudely with six
parts, but five ... ???
No, that's something else. It's described in the original post.
Logic in, output swings from V+ to V+ minus 6 volts, where V+
is pretty big.
I didn't read the op's specs carefully, so my first suggestion
swung V+ to ground (Fred trapped me on that one) but the
limited-swing version can still be done with 5 discretes,
6 if you include current limiting.
John Larkin wrote...
I see, 24 to 50V.
Yes, five.
Yes, assuming V+ current limiting only, and all loads to the
most negative output voltage. Crude, but workable.
