different between rise time ,fall time and turn on delay, turn off delay intransistor

[nxt_]

dear all,
Greetings, i want to know the difference between rise time ,fall time and turn on delay, turn off delay in transistors. and how it affects something like speed control motors. i mean if i need the motor to be run at specific frequency and my delay is 10ns for this particular frequency. do i have to look in the transistor's datasheet and check for the rise & fall time so that i can add extra delay for the switching to get the exact frequenct?! . and what particulary i should look for?! the rise time, fall time. or the turn off,turn on delays?! or both! . kindly tell me how to manage this. and if there is an specific equations to do that i'll appericiate that.

Reagrds,

 

[dick_freebird]

These times will set things like minimum on / off time, add some duty cycle
distortion / limits. Rise / fall times as a fraction of period are a good indicator
of switching losses. But datasheet attributes are also very dependent on the
conditions, and your power stage may or may not bear much resemblance.
Particularly, "small signal" vs "switching" transistors and applications will
differ particularly in things like saturation & recovery (turnoff) behavior,
and this region is very dependent on bias and temperature (for BJTs),