dual gate n-chan MOSFETs

L

Leon Sorokin

Guest
i'm making a lighting system where i need lights to be independently turned
on and off, or at the flip of a switch, have all of them constant on. will
an N-channel dual-gate MOSFET do the trick? if so, does anyone know of one
that can support approx 500ma from drain to source?

otherwise i need to use OR gates, which is an extra IC that i would rather
not use, since i have limited board space. so i am hoping that the dual
gates on the MOSFET are isolated from each other, otherwise it wouldnt make
much sense, right? and i'm also hoping i can find one that can support the
500ma current. well, it'll probably be a 450-500ma 3Hz 3.4V pulse. not a
constant on.

thanks.
Leon
 
Leon Sorokin wrote...
i'm making a lighting system where i need lights to be independently turned
on and off, or at the flip of a switch, have all of them constant on. will
an N-channel dual-gate MOSFET do the trick? if so, does anyone know of one
that can support approx 500ma from drain to source?

otherwise i need to use OR gates, which is an extra IC that i would rather
not use, since i have limited board space. so i am hoping that the dual
gates on the MOSFET are isolated from each other, otherwise it wouldnt make
much sense, right? and i'm also hoping i can find one that can support the
500ma current. well, it'll probably be a 450-500ma 3Hz 3.4V pulse. not a
constant on.
What are you switching, exactly? You can use two mosfets in series.


--
Thanks,
- Win

(email: use hill_at_rowland-dotties-org for now)
 
In article <415ddd58$1_2@newspeer2.tds.net>,
Leon Sorokin <lsorokin@tds.net> wrote:
they're LED clusters, i'm using a 4017 BCD counter to cycle through them,
but i also need the option of having all of them on at the same time through
a switch - there's a flashing mode, and a constant on mode, so i need
isolated gates, so all the gate1s stay separate but all gate2s are joined,
but isolated from all the gate1s. forget the 3hz pulse and 500 ma, i'm
mixing projects : ). the current is around 100ma tho cause i'm using 5 leds
per cluster in parallel and their typical Vf is 3.6V@30ma, so it does need
to support maybe at least 150ma draind source current.
Suggestions:

Drop the 4017 and use a 22V10 and program all the different modes into it.

Use a PIC.

For all LEDs on, connect the Vss of the 4017 to the VCC so that all
outputs are high. For all off ground both. For flashing alternate
between the two.

Use an 8051 to do that and play music while it happens.


--
--
kensmith@rahul.net forging knowledge
 
On Sat, 02 Oct 2004 07:08:16 GMT, "Kevin Aylward"
<salesEXTRACT@anasoft.co.uk> wrote:

John Larkin wrote:

And why not put some of those LEDs in series and save a lot of power?

John

Ahmmm.. Care to look at that statement again:)
No.

John
 
On Sat, 02 Oct 2004 11:34:04 -0700, John Larkin
<jjlarkin@highlandSNIPtechTHISnologyPLEASE.com> wrote:

On Sat, 02 Oct 2004 07:08:16 GMT, "Kevin Aylward"
salesEXTRACT@anasoft.co.uk> wrote:

John Larkin wrote:

And why not put some of those LEDs in series and save a lot of power?

John

Ahmmm.. Care to look at that statement again:)


No.
Hehe! Kevin still getting confused over basic physics? ;-)
--

"What is now proved was once only imagin'd." - William Blake, 1793.
 
In article <aartl05fqjltaqv1j0fjg636of684m1cnn@4ax.com>,
John Fields <jfields@austininstruments.com> wrote:
[...]
2. You shouldn't be using the MOSFETs as source followers.
Also, the driver section doesn't need more than:

3 Resistors
2 Capacitors
1 CD4011
1 CD4017
1 2 Pole 4 position switch

With this you can get the gate drive needed for the following modes:

1 All off
2 All on
3 Blink in turn
4 All blink together.


If you run the CD40XX stuff from a >9V supply, the gate drive will be
enough that you don't need "logic level" MOSFETs and can use the lower
cost ones.
--
--
kensmith@rahul.net forging knowledge
 

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