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No output from 7905 when in increased current..

by ElectroPhysics
Tags: 7905, current, increased, output
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ElectroPhysics
#1
Mar6-12, 03:55 AM
P: 113
Hi. no output from 7905 when configured in high current mode and parallel transistor short circuit protection. please see the attachment for circuit diagram. the load connected to the output is 100 ohm (50mA).
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berkeman
#2
Mar6-12, 11:36 AM
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Quote Quote by ElectroPhysics View Post
Hi. no output from 7905 when configured in high current mode and parallel transistor short circuit protection. please see the attachment for circuit diagram. the load connected to the output is 100 ohm (50mA).
The LM7905 is a negative voltage regulator. So Q1 is backwards, and your polar capacitors are upside-down. You should also show the ground connection on the 7905.
berkeman
#3
Mar6-12, 11:45 AM
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Actually, a bunch of stuff looks wrong in that circuit. Where did you get it?

ElectroPhysics
#4
Mar6-12, 09:37 PM
P: 113
No output from 7905 when in increased current..

some corrections made. the problem is as mentioned before.
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no output from 7905.JPG  
berkeman
#5
Mar7-12, 11:43 AM
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some corrections made. the problem is as mentioned before.
If you hook it up as just a plain 3-terminal regulator without the extra dropping transistor, does it work?
ElectroPhysics
#6
Mar8-12, 04:38 AM
P: 113
Quote Quote by berkeman View Post
dropping transistor, does it work?
the project is in freeze stage as soon as i finish it i will let forum know about the results.
ElectroPhysics
#7
Mar12-12, 09:44 AM
P: 113
7905 was damaged! i replaced it and initial test shows the circuit is working.


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