Power a 9 volt radio from a Makita 18 volt battery

[spec]

Post Issue 03 of 2016_11_24

Hi makdab,

Below is a simple cutoff circuit which uses thru-hole components, apart from the PMOSFET which is surface mount, but it is a big surface mount, so the circuit should be easy to build.

spec

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DATASHEETS
(1) http://www.st.com/content/ccc/resou...df/jcr:content/translations/en.DM00101433.pdf
(2) http://www.fairchildsemi.com/datasheets/BC/BC547.pdf
(3) http://cds.linear.com/docs/en/datasheet/1634ff.pdf

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[Makdab]

Wow Spec,
Really appreciate that. No excuses now

 

[spec]

Wow Spec,
Really appreciate that. No excuses now

No probs Makdab,

I just hope the circuit works OK- it should.

I haven't included the the decoupling capacitors to keep the schematic simple- you need a 22uF ceramic capacitor, with a 30V, or higher working voltage, and X7R dielectric, +- 10% tolerance or better.The 22uF capacitor should connect neat the PMOSFET source and the corresponding 0V point.

Also get a couple of 100nF capacitors- same specification as the 22uF otherwise.

The funny looking resistor in the gate of the PMOSFET should be mounted directly to the gate terminal of the PMOSFET to ensure frequency stability.

spec

 

[Makdab]

Also get a couple of 100nF capacitors- same specification as the 22uF otherwise.

spec

I didn't quite get this bit. Where do the 100's go or do you mean instead of the 22?

 

[spec]

I didn't quite get this bit. Where do the 100's go or do you mean instead of the 22?

Don't worry about that for the moment; I will show the position of all capacitors on a revised schematic.

spec

 

[Makdab]

Ah ok, thank you

 

[spec]

No sweat.

spec