Communities

Writing
Writing
Codidact Meta
Codidact Meta
The Great Outdoors
The Great Outdoors
Photography & Video
Photography & Video
Scientific Speculation
Scientific Speculation
Cooking
Cooking
Electrical Engineering
Electrical Engineering
Judaism
Judaism
Languages & Linguistics
Languages & Linguistics
Software Development
Software Development
Mathematics
Mathematics
Christianity
Christianity
Code Golf
Code Golf
Music
Music
Physics
Physics
Linux Systems
Linux Systems
Power Users
Power Users
Tabletop RPGs
Tabletop RPGs
Community Proposals
Community Proposals
tag:snake search within a tag
answers:0 unanswered questions
user:xxxx search by author id
score:0.5 posts with 0.5+ score
"snake oil" exact phrase
votes:4 posts with 4+ votes
created:<1w created < 1 week ago
post_type:xxxx type of post
Search help
Notifications
Mark all as read See all your notifications »
Q&A

Comments on PNP Darlington pair as a current limiter

Post

PNP Darlington pair as a current limiter

+5
−0

I am trying to analyse what is controlling the load current in the below Darlington configuration.

  1. Is it the base current of transistor Q3 which is controlling current through R14 / emitter current of Q2?

Image alt text

  1. If it is, then is the maximum permissible load current is calculated by Ic(Q3) * Q1 beta * Q2 beta ?

  2. From light load to maximum load, will all three transistor stay in the active region? For light loads , Q2 may get into saturation region I suppose.

EDIT : Alternate circuit to achieve the same functionality

Image alt text

are there any drawbacks to use this circuit ?

History
Why does this post require attention from curators or moderators?
You might want to add some details to your flag.
Why should this post be closed?

1 comment thread

A few problems with this post. (4 comments)
A few problems with this post.
Olin Lathrop‭ wrote almost 3 years ago · edited almost 3 years ago

What's with the stars in the title? Trying to be special at the expense of others is not cool. I deleted them. Don't do that again.

We shouldn't have to tilt our heads to read a schematic. Rotated labels are annoying. Also, try to keep high voltage at top, low voltages at bottom, and logical flow left to right.

I can't guess what "150" is supposed to mean for V3, nor what V3 even is in the first place. The name implies a voltage source. The "+" and "-" show polarity, but the "~" implies AC. You are new here, so I let this slide temporarily. I expect you to fix this within a day.

This site is a great place to get good electrical engineering help, but you have to do your part and respect the people providing that free help. We require questions to be clear, concise, and in proper engineering style. Trying to be special, sloppiness (you're not guilty of that one), and disregard for proper units will get you tarred and feathered out of town.

kadamrohan16‭ wrote almost 3 years ago

Respected Sir , First of all , I sincerely apologize for all the mistakes made by me . This is my first on this forum and I assure you that I will keep in mind all the rules and process hence forth. I am following you from electronic stack exchange forum and highly admire you for your great knowledge. I consider my self lucky to be able to gain knowledge from highly intellectuals like you and others . I have made all necessary changes in the question post .

Olin Lathrop‭ wrote almost 3 years ago · edited almost 3 years ago

Your updated schematic is much better. I guess we can put the tars and feathers back in the closet now :-)

Andy aka‭ wrote almost 3 years ago · edited almost 3 years ago

@olin - keep them ready and warmed-up for the next bad post. In case anyone thinks Olin is being harsh, he's not. A little bite at a person's ankles to remind them what is expected of a good question isn't being unnecessarily rude; engineering requires absolute attention to detail if you are to be good at it and, that covers the whole gamut from analysing contracts through design, test to product delivery. Sloppiness is something to be avoided. OK we all screw up now and then and a little pointed reminder will do someone a favour if they are truly interested in engineering. If someone corrects any of my mistakes in what some people might think is a rude manner it's not a problem because, the corrector is doing you a big favour. It's a shame that stack exchange puts so-called impolite behaviour as such a high offence compared to the great service done in forthrightly helping someone see their errors. Engineering isn't for fools.