- #1
No output from 7905 when in increased current
Click For Summary
Discussion Overview
The discussion revolves around troubleshooting a circuit involving the LM7905 negative voltage regulator configured for high current operation with parallel transistor short circuit protection. Participants explore issues related to circuit design and functionality, including component orientation and connections.
Discussion Character
- Technical explanation, Debate/contested
Main Points Raised
- One participant notes that the LM7905 is a negative voltage regulator and points out that Q1 is connected backwards, and the polar capacitors are incorrectly oriented.
- Another participant questions the overall correctness of the circuit design and asks for the source of the circuit diagram.
- A later reply indicates that corrections were made but maintains that the original problem persists.
- One participant suggests testing the circuit as a standard 3-terminal regulator without the additional dropping transistor to see if it functions correctly.
- A subsequent post reveals that the LM7905 was damaged, but after replacement, initial tests indicate that the circuit is now working.
Areas of Agreement / Disagreement
Participants express differing views on the correctness of the circuit design, with some identifying specific issues while others question the overall setup. The discussion includes both corrections and ongoing uncertainty about the initial problem.
Contextual Notes
Limitations include unresolved questions about the circuit's design integrity and the implications of the identified errors on functionality. The discussion does not clarify whether all proposed corrections were implemented successfully.
- #2
berkeman
Admin
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ElectroPhysics said:
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.
- #3
berkeman
Admin
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- 25,128
Actually, a bunch of stuff looks wrong in that circuit. Where did you get it?
- #4
- #5
berkeman
Admin
- 69,539
- 25,128
ElectroPhysics said:
If you hook it up as just a plain 3-terminal regulator without the extra dropping transistor, does it work?
- #6
ElectroPhysics
- 115
- 2
berkeman said:
the project is in freeze stage as soon as i finish it i will let forum know about the results.
- #7
ElectroPhysics
- 115
- 2
7905 was damaged! i replaced it and initial test shows the circuit is working.
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