Low Current Sensing Technique

[zaighum mir]

Hello Everyone,
I am looking for a method of low current sensing. I need to measure the leakage current of Mosfet but i am not able to find any sensor or module to measure current in nano amps. Can anyone guide me on this?

 

[KlausST]

Hi,

I guess low voltage DC. Please confirm.

If so then a resistor to convert current to voltage is a valid method.
Maybe combined with an Opamp. Look for "TIA circuit".
Please define voltage, current_range, expected accuracy and resolution.

Klaus

 

[dick_freebird]

You can find benchtop picoammeters in most major
test instrument mfrs' product lines although they are
a niche function.

You could build your own with an op amp and
precision resistor, transimpedance style and use
a generic DMM on the output voltage. Need to
get a good CMOS or JFET input op amp for high
Zin, and perhaps some care with PCB design.

A really crude option is a precharged capacitor
and timer, I=C*dV/dt. Take an open socket reading
to get at any fixture current which would be
superimposed. You could use a 'scope probe
(although its 10Mohms will perhaps dwarf the
leakage current of interest) to get the time for
dV=1V, or whatever.

 

[danadakk]

Alan Yates' Laboratory - Picoammeter

http://circuitcellar.com/wp-content/uploads/2014/03/CC_042010_Lacoste_ReprintedwPermission-web.pdf

Picoammeter circuit with 4 ranges - circuit diagrams, schematics, electronic projects

www.diy-electronic-projects.com

Picoammeter Design - Page 1

Picoammeter Design - Page 1

eevblog.com

Regards, Dana.