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Help requested for a circuit design

Spacial

Jun 28, 2014
1
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Jun 28, 2014
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Be really grateful for any suggested solution to this problem

2qd4l51.jpg
 

KrisBlueNZ

Sadly passed away in 2015
Nov 28, 2011
8,393
Joined
Nov 28, 2011
Messages
8,393
Your circuit is drawn upside down. It's normal to draw the 0V rail across the bottom.

There is no need for the 2k2 base resistor.

You can get the behaviour you want by connecting a diode with its cathode to the negative side of the capacitor and its anode connected to the 0V rail.

Depending on what is meant by "power is removed", you may need to add a resistor across the power supply rails as well; the lower this resistor is, the more quickly the capacitor will discharge when power is removed. If you're not concerned about wasting current, I suggest 0.1W dissipation in this resistor (so you can use a standard 1/4W component); in this case R = V2 / P = 144 / 0.1 = 1.44 kilohms; use 1k5.

Edit: The "pulse" produced by this circuit is not rectangular. I know the specification doesn't define the shape required, but you could get a cleaner output with no extra components if you use the transistor in common emitter configuration rather than emitter follower. Let us know if you want to see a schematic.
 
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