Saturation in circuit

Jynne

Joined Aug 2, 2004
1
Newbie Here

This is the question I am having trouble with. I am unsure of what formula I would use to figure out the value of R2. I think I have part 1 of the question right, but I will post it all because it might be needed to answer the R2 question.

Part 1
If Vcc is 15V and you want an IB of 75μA, what value should you have for R1?
I used the formula Vcc-Vbe(IB) and came up with 191kΩ.

Part 2
Using the 75μA as IB and βdc of 150, what value R2 is necessary to produce saturation in this circuit?

Any help regarding the formula I should use would be appreciated!

Thanks

mozikluv

Joined Jan 22, 2004
1,435
hi,

i would like to answer you query but your presentation is not clear. i will assume that your R1 is connected to the supply rail and to the base for a 75uA Ib. now the R2 is not clear where it is to be placed, is it to be a base current stabilizer or is it the collector load. maybe it you had posted your circuit things would had been simpler to reply.

at 75uA with a hfe of 150 will theritically produce 11ma at the collector. any current value that you inject at the base as long as it is within the spec will make your transistor conduct, likewise with the voltage. to make sure that your transistor will conduct a voltage of 0.7v will suffice.