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Optoisolator Circuit

WaltP

Jun 16, 2017
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Hi. I'm a bit of a newbie slowly working my way up the learning curve. Could someone please help with a circuit and choice of transistor to increase the current output from a proximity sensor (LCZ260) in order to trigger an opto isolator - I'm using a 6N137. The proximity sensor output at 5 volts is .5 to 1.1 ma depending on resistor choice which I need to boost to around 10 ma in order to trigger the 6N137. Thanks in advance.

Walt
 

AnalogKid

Jun 10, 2015
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Can't draw a sch right now.

2N7000 or 7002 MOSFET:
Sensor output to gate
Source to GND
Drain to 6N137 cathode
6N137 anode to 220 ohm resistor.
220 ohm resistor to +5 V.

2N4401, 3904, 2222 Bipolar transistor:
Sensor output to 1K resistor
1K resistor to NPN transistor base
Transistor emitter to GND
Collector to 6N137 cathode
6N137 anode to 220 ohm resistor
220 ohm resistor to +5 V

ak
 

WaltP

Jun 16, 2017
10
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Jun 16, 2017
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Many thanks, I'll give it a run.

Edit: Happen to have a 2N7000 and it worked quite nicely. Changed to a 560 ohm resistor which put me at 10 ma. Again, thanks for for help. If you feel like responding again, is there any advantage or disadvantage to a mosfet. If I interpreted the datasheet correctly, response time seems faster at lower voltages which, I think, would be in the 20 nanosecond range. Are bipolar transistors faster?

Walt
 
Last edited:

Minder

Apr 24, 2015
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One advantage of a mosfet is it offers high input impedance over bi-polar.
M.
 

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(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
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One disadvantage of the MOSFET is it's high input impedance.

Ok, that's a bit tongue in cheek, but the differences between components can be advantageous or detrimental. They are almost always a double edged sword.
 

Minder

Apr 24, 2015
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I vary rarely use bi-polar transistors any more if I can help it.
M.
 

BobK

Jan 5, 2010
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Bipolar transistors behave better when doped with Lithium.

Bob
 
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