Vout & Short Circuit Output Current: Need Help!

Click For Summary
SUMMARY

The discussion focuses on calculating the open circuit output voltage (Vout) and estimating the short circuit output current for the LT1084C voltage regulator. Participants emphasize the importance of consulting the LT1084C datasheet to understand its operational characteristics, particularly regarding the transistor Q1, which is likely used for overload protection. Key calculations involve the resistor values R1 and R2, as well as the relationship between Vout and the voltage at the ADJ pin. For short circuit current, the specifications in the datasheet provide the necessary information.

PREREQUISITES
  • Understanding of voltage regulators, specifically the LT1084C model.
  • Familiarity with basic electrical principles, including Ohm's Law (V=IR).
  • Knowledge of circuit components, particularly transistors and their functions in overload protection.
  • Ability to read and interpret electronic component datasheets.
NEXT STEPS
  • Download and analyze the LT1084C datasheet for detailed specifications.
  • Research the role of transistors in voltage regulation and overload protection.
  • Learn about calculating output voltage in voltage regulators using resistor values.
  • Investigate methods for estimating short circuit current in electronic circuits.
USEFUL FOR

Electronics students, engineers working with voltage regulators, and hobbyists designing power supply circuits will benefit from this discussion.

shaqtus
Messages
7
Reaction score
0

Homework Statement


Here is the problem: http://img507.imageshack.us/img507/6488/unled2b.jpg

What is the open circuit output voltage, Vout?
Estimate the short circuit output current

Can someone explain to me how to do these.

Homework Equations



Honestly... no idea. I know V=IR and all that but it doesn't seem to help here.

The Attempt at a Solution

 
Last edited by a moderator:
Physics news on Phys.org
You'll have to look up the characteristics of the LT1084C regulator to see how it operates. Perhaps download a datasheet.

The transistor Q1 looks like it might be for overload (short circuit?) protection. Its base bias resistors are in the path of the load current (returning back to the bridge rectifier). After some load current threshold it's going to turn on and pull the regulator's Adj pin low, dropping the output voltage. You should probably look into what load current will cause the transistor to turn on and start to pull the output voltage down.
 
For OC output voltage Vout, all you need is the values of R1, R2 and the mfr's spec on the relationship between Vout and the voltage at the ADJ pin.

For SC current, I'd look at the spec sheet for that info.
 

Similar threads

  • · Replies 1 ·
Replies
1
Views
2K
Replies
15
Views
3K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 7 ·
Replies
7
Views
3K
  • · Replies 1 ·
Replies
1
Views
4K
  • · Replies 4 ·
Replies
4
Views
6K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 34 ·
2
Replies
34
Views
6K