Hi Greg.

02-Jan-04 08:17:00, Greg Mayman wrote to Roy J. Tellason



 GM>> It's time to set up for some DC tests with a power supply and
 GM>> resistors, and see if they act like NPN transistors.

 RJT>> Don't need a power supply and resistors -- testing with an
 RJT>> ohmmeter is quite enough.

 GM> DC tests can show you which is collector and which emiter -- the
 GM> base-emiter usually shows a reverse breakdown of about 6-8 volts,
 GM> the collector-base junction is a lot higher. There aren't many
 GM> ohmmeters that can check these aspects.

something like this can give an indication....

  C      ohmmeter probe-1
                    ___      |
                   __|__     |
  B    <---[100K]--o   o-----'

  E      ohmmeter probe-2

with the trasistor correctly connectted a larger deflection is evident when
the button is pressed, swapping ohmmeter probes allows testing of PNP or
NPN trasistors.

 GM> And with DC tests you can measure the current gain of the
 GM> transistor, which you can't do with an ohmmeter...

 yeah, there is that... but by disconnecting the collector lead and
 pressing the button, and the reconnecting it and testing  the ratio
 difference in reading gives some sort of indication...

 -=> Bye <=-

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