No output from 7905 when in increased current

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ElectroPhysics
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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).
 
Attachments
  • Circuit schematic of a negative voltage regulator with a 7905 IC (U1) and two TIP31 pass transistors (Q1, Q2) for boosted current, with resistors R1 (0.68) and R2, and capacitors C1 (0.22u), C3 (33p) and C2 (220u).
    no output from 7905.JPG
    8.5 KB · Views: 627
ElectroPhysics said:
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.
 
Actually, a bunch of stuff looks wrong in that circuit. Where did you get it?
 
some corrections made. the problem is as mentioned before.
 
Attachments
  • Circuit schematic of a negative voltage regulator using an LM7905 with two TIP31 pass transistors (Q1, Q2), resistors R1 0.68 and R2, capacitors C1 0.22u, C2 220u and C3 33p, and a -12V input.
    no output from 7905.JPG
    8.6 KB · Views: 605
ElectroPhysics said:
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?
 
berkeman said:
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.
 
7905 was damaged! i replaced it and initial test shows the circuit is working.