• Support PF! Buy your school textbooks, materials and every day products Here!

Circuit diagram to analyze that looks wrong to me

  • Engineering
  • Thread starter dumguy
  • Start date
  • #1
12
0
I have a circuit diagram to analyze that looks wrong to me. It is fairly straight forward and I will attempt to describe it. It is an unlabelled power source with the neg terminal feeding a photocell, that part I understand. Here is the problem, that same neg branch of the circuit also feeds into the collector terminal of an NPN transistor with the base terminal of the NPN transistor receiving the switched neg fom the photodiode. It appears the intention of the design was to use the photodiode to switch the transistor which switches a light. Kind of like how the steet lights come on at dark. My question is, can an NPN transistor function with this bias, neg to collector, switched neg to base and pos side of light bulb connected to emmitter?
 

Answers and Replies

  • #2
NoTime
Science Advisor
Homework Helper
1,568
0
What are the two classes of bi-polar transistor?
 
  • #3
12
0
NPN and PNP
 
  • #4
NoTime
Science Advisor
Homework Helper
1,568
0
Ok, which one is your project using?
 
  • #5
12
0
npn by the symbol
 
  • #6
NoTime
Science Advisor
Homework Helper
1,568
0
From your description this doesn't sound correct.
Perhaps you should post the schematic.
 
  • #7
12
0
circuit diagram
 

Attachments

  • #8
berkeman
Mentor
56,656
6,559
Circuit looks wrong, or it's a trick question (like the answer is "never").

The load should be directly connected to the collector, and the voltage source should have + on top of the load, and - down on the emitter. The cathode of the photodiode should also connect above the load to the + supply.
 
  • #9
NoTime
Science Advisor
Homework Helper
1,568
0
In this case it looks like the battery symbol is backwards.
The same issue applies to the photodiode as well as the transistor.

Edit: You beat me to it B, I considered the "never" answer as well :smile:
 
Last edited:
  • #10
12
0
Thanks to all that took the time to have a look at this thing. My text is full of misprints and omissions.
 

Related Threads for: Circuit diagram to analyze that looks wrong to me

Replies
5
Views
1K
Replies
2
Views
803
Replies
10
Views
1K
Replies
0
Views
3K
Replies
10
Views
2K
Replies
6
Views
3K
Top