00:01
So let us start with the concept which we are going to use here for this question.
00:08
Since we know for the transistor or npn transistor the current ic is nothing but equals to vcc minus vce saturation divided by the resistance rm.
00:22
So we have to design the circuit by using npn transistor as a switch control by the wind motor with the resistance of rm is equals to 48 ohm by using 3 .3v of logic state.
00:37
Now beta we have been given equals to 140, vce saturation volt is given 0 .1v and we have to control the 12v of the motor.
00:49
Right, so this much of the values have been given.
00:53
So let us calculate first the collector current ic.
00:56
So this can be given by vcc minus vce saturation divided by the rm.
01:03
So this can be goes to so vc will be 12v.
01:07
Right, minus vce saturation we have been given 0 .1 divided by the rm we have been given 48 ohm.
01:14
It will be comes out equals to near about 248 ma.
01:20
So this is what the required current ic for the designing.
01:25
Then the minimum base current ib minimum this can be equals to keep the transistor in saturation region.
01:35
So this is given by ic by beta and hence this will be goes to 0 .248 divided by beta is 140 will comes out 1 .7714 of ma.
01:47
This is what the second factor for designing.
01:51
Now the required base current would be ib of should be greater than equals to 4 times of this ib minimum.
02:01
Right, and hence ib will be greater than equals to 4 times of 0 .0017714.
02:10
So, ib should be greater than equals to 7 .0857 of ma.
02:16
So greater than equals to this much that means we can take ib equals to 7 .1 of ma.
02:24
So this is what one of the factor of the our designing...