Transistor-LED circuit problem

Thread Starter

RedRatchet

Joined Sep 2, 2019
1
Im struggling with this problem, specially with the transistor.
Problem ask for:
R2 for max light on LED at night
R1 for correct working
Can LED work at day light?
1.png 6a476538a077f1b4eaa30504a2e1ff99.png 2.png

My problem is: For R2 i assumed T1 on saturation, then i design R2 for 10mA, so i got 920 ohms. Im stuck at this point, dont know how to use/prove saturation or active T1.
 

danadak

Joined Mar 10, 2018
3,506
Rule of thumb for sat is Ibase = Icollector/10. This is also referred to as
forced beta.

Example curve from a transistor -

upload_2019-9-2_8-46-8.png

Regards, Dana.
 
Top