Substituting NFET for PFETS?

Guest
I'm wondering if someone could please help out a novice...

I'm trying to build the following circuit, but my local supplier, RadShack,
only carries N-Channel FETS, not P-Channel as specified by the schematic.
Can someone recommend a simple solution with NFETS, or perhaps an
alternative altogether.

Here is the circuit: http://www.animalrushhour.com/brad/pfetcircuit.gif

Which is actually part of this document regarding driving higher current
LEDS with the MAX7219:
http://www.maxim-ic.com/appnotes.cfm/appnote_number/1196

Thanks!

-Brad
 
test wrote:
I'm wondering if someone could please help out a novice...

I'm trying to build the following circuit, but my local supplier,
RadShack, only carries N-Channel FETS, not P-Channel as specified by
the schematic. Can someone recommend a simple solution with NFETS, or
perhaps an alternative altogether.

Here is the circuit:
http://www.animalrushhour.com/brad/pfetcircuit.gif

Which is actually part of this document regarding driving higher
current LEDS with the MAX7219:
http://www.maxim-ic.com/appnotes.cfm/appnote_number/1196

Thanks!

-Brad
Click to expand...
Brad, you can also save a lot of money taking these bipolar PNP transistors
instead. They can switch around 100mA max.
If the driver voltage is higher, you can insert a cascode stage similar to
the drawing in the data sheet.


Vdriver
+--------+----------o
| | less than 10V
.-. |
1k| | |
| | |
'-' |
| |<
+------| 2N3906
| |\
.-. |
1.8k| | |
| | anode digit drive
'-'
|
o
Dig0...Dig7



Vdriver
+--------+----------o
| | more than 8V
.-. |
1k| | |
| | |
'-' E|
| |<
+------| 2N3906
| B |\
.-. |C
| | |
1k| | anode digit drive
'-'
|C
|/
+5V o------| 2N3904
B |>
E|
.-.
| |
1k| |
'-'
|
o------+
Dig0...
created by Andy´s ASCII-Circuit v1.22.310103 Beta www.tech-chat.de

ciao Ban
 
That looks like the advice I was looking for. I'm pretty good with digital
electronics, but analog still holds many mysteries for me.

Thanks!


"Ban" <bansuri@web.de> wrote in message
news:fobZa.35218$an6.1230097@news1.tin.it...
test wrote:
I'm wondering if someone could please help out a novice...

I'm trying to build the following circuit, but my local supplier,
RadShack, only carries N-Channel FETS, not P-Channel as specified by
the schematic. Can someone recommend a simple solution with NFETS, or
perhaps an alternative altogether.

Here is the circuit:
http://www.animalrushhour.com/brad/pfetcircuit.gif

Which is actually part of this document regarding driving higher
current LEDS with the MAX7219:
http://www.maxim-ic.com/appnotes.cfm/appnote_number/1196

Thanks!

-Brad

Brad, you can also save a lot of money taking these bipolar PNP
transistors
instead. They can switch around 100mA max.
If the driver voltage is higher, you can insert a cascode stage similar to
the drawing in the data sheet.


Vdriver
+--------+----------o
| | less than 10V
.-. |
1k| | |
| | |
'-' |
| |
+------| 2N3906
| |\
.-. |
1.8k| | |
| | anode digit drive
'-'
|
o
Dig0...Dig7



Vdriver
+--------+----------o
| | more than 8V
.-. |
1k| | |
| | |
'-' E|
| |
+------| 2N3906
| B |\
.-. |C
| | |
1k| | anode digit drive
'-'
|C
|/
+5V o------| 2N3904
B |
E|
.-.
| |
1k| |
'-'
|
o------+
Dig0...
created by Andy´s ASCII-Circuit v1.22.310103 Beta www.tech-chat.de

ciao Ban
Click to expand...
 
Use one of these for Q2.

Radio shack P#
900-5549 VP0300L Vds= -30V Id= 0.320 Amp TO-92 $.99
900-5548 VP0300B Vds= -30V Id= 1.250 Amp TO-39 $6.59
900-5194 IRF9510 Vds= -100V Id= 4.0 Amp TO-220
$1.16

You can order it from your local R/S or call 1 800 442 7221

Good luck,
Cyrus
( please reply to group )

<test> wrote in message news:vja90e8qml3862@corp.supernews.com...
I'm wondering if someone could please help out a novice...

I'm trying to build the following circuit, but my local supplier,
RadShack,
only carries N-Channel FETS, not P-Channel as specified by the schematic.
Can someone recommend a simple solution with NFETS, or perhaps an
alternative altogether.

Here is the circuit: http://www.animalrushhour.com/brad/pfetcircuit.gif

Which is actually part of this document regarding driving higher current
LEDS with the MAX7219:
http://www.maxim-ic.com/appnotes.cfm/appnote_number/1196

Thanks!

-Brad
Click to expand...
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top