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Old 11th September 2014, 07:50 AM   #1
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Default transistor hfe help

hi,
is it possible to use two transistor constant current source circuit to supply constant current to the transistor base what is being tested.
construct multiple constant current source circuit ranging from micro amps to few milli amps and use rotary switch to select the current we want.
simply use two digital ammeter to measure base and collector current.

will it work?
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Old 11th September 2014, 08:54 AM   #2
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Hfe is the ratio between the collector current and base current. For example for a power transistor with an Hfe of 70, means that to pass 70mA of collector current 1mA of base current is required. So, to have a constant current supply for the base, selectable as you suggest and measure the collector current, makes perfect sense. The only drawback is knowing the power handling of the device under test and adjust manually as required to avoid damaging the device when testing.
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Old 11th September 2014, 09:24 AM   #3
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Quote:
Originally Posted by JonSnell Electronic View Post
Hfe is the ratio between the collector current and base current. For example for a power transistor with an Hfe of 70, means that to pass 70mA of collector current 1mA of base current is required. So, to have a constant current supply for the base, selectable as you suggest and measure the collector current, makes perfect sense. The only drawback is knowing the power handling of the device under test and adjust manually as required to avoid damaging the device when testing.
yes transistor data sheet must be used as a guide to avoid device damage.
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Old 11th September 2014, 10:16 AM   #4
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Worth bearing in mind that hfe does vary with VCE, so some way of controlling VCE might be a good idea.
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