Question

+12V Solenoid coil fesis tunce Trunsrstor TIP41C Switeh Ouerdnive fecter of 10 TIP41C Ca leulate the lve of R neededl for relcble Sithang

Answer 1

Answer:

The saturation collector current with 100 ohm load computed as

Ic(sat) = (Vcc - Vce(sat) )/Rload

From the datasheet of TIP41C we note that Vce(sat) = 1.5V

Therefore

Ic(sat) = (12-1.5)/100 = 0.105 or 105mA

To drive this collector current we would need a base current Ib(sat) of

Ib(sat) = Ic(sat)/beta = 105/80 = 1.31mA

Next, Over drive factor (ODF) is defined as

ODF = Ib/Ib(sat)

Therefore required Ib is

Ib = 1.31*10 = 13.1mA

This enables us to compute the value of R in the following manner:

12 = Ib*R + Vbe

We take the typical value of Vbe as 0.7V, then

R = (12 - 0.7)/13.1 = 0.862 K ohm (as the current is in mA), or

R = 862 Ohm

Hope this helps