How to get hFE value?

Use 200 for that transistor.

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Measure the voltage on the collector, subtract that voltage from the
supply voltage and divide that by the collector resistor\'s
resistance.  That will be the collector current.  Call it Ic.

Measure the voltage on the base, subtract that voltage from the
supply voltage and divide that by the base resistor\'s resistance.
That will be the base current.  Call it Ib.

Divide Ic by Ib.  The quotient will be beta.

Extrapolate using the data sheet. Which says, btw, that at I(c)=150mA, V(ce)=10V, min hfe=100, max hfe=300. Hence the previous poster's suggestion to use 200.

hfe varies with current, voltage, temperature, etc. Generally highest around the mid-point of voltage and current ranges, lower towards the ends.

"NoClue"

** Honest at least ....

** You cannot.

Hfe is a variable parameter of *actual devices* - it varies widely from sample to sample and is also significantly affected by the voltage current and temperature levels experienced by that device.

What you have drawn is suitable for TESTING the Hfe figure of individual PN2222 devices - since the base current is fixed and the collector current can be noted from the voltage across Rc.

....... Phil

The simplest and most accurate way to determine the hFE for the transistor you are using is to simply measure the current flowing through Rc and Rb. Then divide Rc/Rb. You could as suggested else-where measure the voltage across the resistors, however you then open yourself to errors when you remember the tolerance values applied to the resistors.

Chris

NoClue wrote:

** Top Posting Groper Alert !!

** Better try Ic / Ib.

** With standard 1% resistors and a decent DMM, the result will be within 1% which is likely to be as good or better than using the same DMM as a current meter.

When matching the Hfe of two or more devices, accurate test figures are irrelevant.

...... Phil