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What BJT specification do I need to look at for switching time?

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FusionITR

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What specification in the datasheet list the time it takes for the collector current to change in reaction to a change in the base current? Ive looked at mulitple datasheets for different transistors and I dont see this time specificed, altough it does matter.

For example, this is my sample circuit:

**broken link removed**

This is what the output is using a 2N2222 transistor:

**broken link removed**

This is what the output looks like using a MPSA05 transistor:

**broken link removed**

Obviously using the MPSA05 transistor, it doesnt react fast enough to the base current going to zero to change the collector current to zero before the base current goes back up.

What specification on a datasheet do I need to look at in general to see if a transistors switching time is good enough for whatever I happen to be working on?

Thanks.
 
What frequency are you using?

You could try a higher frequency unitl like the BF199 or a small MOSFET like 2N7000.
 
The frequency is 15.63Khz but the duty cycle is like 90% so the switching time is very fast compared to the frequency.
 
Look on page 5 of the datasheet.
 

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