Limitations of 4N35 opto?

[RogerTango]

What is the max DC voltage and amps a 4N35 can support please?

How about AC?

Thanks,
Andrew

 

[RadioRon]

Well, it depends on what you mean by support, but I'll make the assumption that you mean across and through the collector to emitter connection, which is typically used as the output. The Vishay 4N35, which I will assume is typical, will tolerate up to 50mA of DC current and up to 100mA for short durations of 1mSec or less. It will tolerate a voltage of up to 70V. It also will only tolerate a combination of current and voltage up to 0.15 Watts (current x voltage = watts).

The AC behavior depends on what shape of AC. The peak current limit would remain the same, 50mA, even though it is going up and down repeatedly and the peak voltage rating would remain the same. The total power that the device could tolerate would have to be adjusted up or down depending on the average RMS voltage multiplied by the RMS current of the AC.

 

[kchriste]

Max DC voltage for the transistor side = 30Vdc
Max transistor current = 100ma
Max LED current = 60ma so the Max transistor current will also be around 60ma.
You can not switch AC with this device alone. Use an TRIAC opto coupler for this.
A useful site:
Datasheets.org.uk :: Datasheet :: 4N35 Semiconductor Data Handbook 1977

 

[RogerTango]

Thank you kindly, very helpful.

I see I can use a 35 for smaller draw loads, or to drive a MOSFET for larger loads.

Take care,
Andrew

 

[MrAl]

Hi,


One important aspect of an opto coupler is its
DC Forward Current Transfer Ratio.

This spec says that if you put in 10ma with a FCTR of 100%
that you will get 10ma collector current. With 50% you only
get 5ma, and with 200% you get 20ma.
You dont want to drive the LED too high either or its lifetime
is significantly lowered and at some point the circuit doesnt
work anymore.

Also, the switching time is really slow for many optos.
This has to be checked also. It speeds up a little with
a base resistor, but that steals some of the drive current
too so it ends up being a tradeoff between speed and
max output current.