I'm screwing around with this one on the workbench.
The 100k seems about right to get the full range of dim to bright at the bulb,
but I don't know if I need to bother with the 5k resistor.
![Darlington circiuit bias 4A bulb.png Darlington circiuit bias 4A bulb.png](https://forum.allaboutcircuits.com/data/attachments/83/83129-ad36f2f68432726b91fec4db26cc74d4.jpg)
Then, I want to apply it to a LM723 voltage regulator, like this:
I see this a lot. Usually, a BD139 into a 2N3055, no resistor bias, or whatever we'd call a
resistor on the base. (Frankly, I'm surprised that works with more than one 2n3055, why?)
Anyway, I'd like to try it with darlingtons. Do I need a resistor in there somewhere,
or does the puny 150ma output of the LM723 negate any worry about frying the bases off the
darlington transistors?
If I try it with a LM317, should a 100 ohm be enough to "bias" this darlington-to-darlington arraignment?
I have a TIP120 driving six TIP102s, all mounted to a heatsink and ready to go. I don't want to fry an afternoons work.
The 100k seems about right to get the full range of dim to bright at the bulb,
but I don't know if I need to bother with the 5k resistor.
![Darlington circiuit bias 4A bulb.png Darlington circiuit bias 4A bulb.png](https://forum.allaboutcircuits.com/data/attachments/83/83129-ad36f2f68432726b91fec4db26cc74d4.jpg)
Then, I want to apply it to a LM723 voltage regulator, like this:
![Darlington circiuit LM723 .png Darlington circiuit LM723 .png](https://forum.allaboutcircuits.com/data/attachments/83/83130-73ef6139c23a6c4662f9281399588c74.jpg)
I see this a lot. Usually, a BD139 into a 2N3055, no resistor bias, or whatever we'd call a
resistor on the base. (Frankly, I'm surprised that works with more than one 2n3055, why?)
Anyway, I'd like to try it with darlingtons. Do I need a resistor in there somewhere,
or does the puny 150ma output of the LM723 negate any worry about frying the bases off the
darlington transistors?
If I try it with a LM317, should a 100 ohm be enough to "bias" this darlington-to-darlington arraignment?
I have a TIP120 driving six TIP102s, all mounted to a heatsink and ready to go. I don't want to fry an afternoons work.