help!! smd transistor's hfe measurement

[oz_gur]

dear all,
hi to all for the first time
i need help for smd transistors. i want to measure hfe values of these to have an statistics' work.
How can i measure it. is there a special tool for it its really hard to measure it on a multimeter that has hfe emasurement for leaded type.

[Harlan]

Hey Oz_Gur

I am not sure if you are asking more of how to connect to the device (ie in circuit or using a jig) or more calculation methods.
But to determine the hFE is rather easy using only current and voltage of the device operating.
Measure the current flow through the Base and the Collector of the device and then calcualte the gain by

I collector
hFE= -------------
I Base

Example:
Transistor is connected to a 12 volt supply, base is biased to 0.65 Volts and measured is 200 ma in the collector, and 2 ma in the base you get results of 200/2 or =100 hFE

Thats the simple way if you dont need extreme accuracy.

I am sure others will have other methods maybe more accurate and simpler too.
Hope this helps
Harlan

[Richard C]

This works:

Take a piece of un-etched copper-clad pcb about 50cm square.

Use a knife to divide the copper into 3 squares with about 1mm seperation (T shaped cut).

Clean the copper thoroughly and wipe the surface with contact cleaner.

Solder a wire loop to each copper surface for connecting to the meter.

By pressing the transistor down (use tweezers) with each pin on a seperate piece of copper it's very easy to measure hfe etc.