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Transitor help required Pls!

S

SME

Hello Group

I wish to reverse the logic from a parallel port output using transistors.
So when the output is high the line into the transistor is high

For example :-

Printport
Collector 12V

/
Base|/
D0 -----|
|\
\
Emitter
|
|
---------Gnd

As I understand it the above circuit when D0 is high (+5V) will sink the
collector bring the 12V input to Low (I understand there should be resisters
in the above circuit etc etc)

As mentioned above I which to have a circuit that when D0 is High the 12V
input is High and when D0 is Low it pulls the 12V input Low.

TIA
Steve.
 
R

Roy J. Tellason

SME said:
Hello Group

I wish to reverse the logic from a parallel port output using transistors.
So when the output is high the line into the transistor is high

For example :-

Printport
Collector 12V

/
Base|/
D0 -----|
|\
\
Emitter
|
|
---------Gnd

As I understand it the above circuit when D0 is high (+5V) will sink the
collector bring the 12V input to Low (I understand there should be resisters
in the above circuit etc etc)

As mentioned above I which to have a circuit that when D0 is High the 12V
input is High and when D0 is Low it pulls the 12V input Low.

TIA
Steve.

Use a PNP transistor with the collector and emitter connections the reverse of
what you've shown here.
 
F

Fritz Schlunder

Roy J. Tellason said:
Use a PNP transistor with the collector and emitter connections the reverse of
what you've shown here.


I don't think that will work. He needs level shifting from the 5V parallel
port logic levels to 12V, but he doesn't want the signal inverted.

A PNP with 12V at the emitter and 5V or 0V at the base (through a resistor)
will never turn off.

Depending upon your requirements it might be possible to use some device
like the 7407 to perform this function, however the 7407 does need a 5V
supply as well (that ideally should be of equal to or slightly larger
magnitude than the 0-5V swing of your parallel port). Datasheet at:

http://www.fairchildsemi.com/ds/DM/DM7407.pdf

Alternatively you can use two of those single transistor inverters in series
so the signal is no longer inverted.
 
B

Ban

SME wrote:
|| Hello Group
||
|| I wish to reverse the logic from a parallel port output using
|| transistors. So when the output is high the line into the transistor
|| is high
||

view with fixed font:

+5V
|
.-.
| |
2k2-10k| |
'-'
| open collector
+-----+ o
1.2V-5V CMOS | | |
___ |/ | |/
o-|___|--|2N3904 +---|2N3904
10k |> |>
| |
| |
=== ===
GND GND
created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de

ciao Ban
 
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