Phase 4 Electronics Question Help!!!

RJ59

Measurements taken in a transistor circuit gave the following results

IE=50.01mA
IC=0.50 mA
VCC=0.30V

From the results obtained, determine the current in the base??

wrecking my head i cant formula for it:rolleyes:

.G.

It should be in the electronics formulas on your sheet under bi polar transistors.

Formula is Emitter current(IE)=Ic +Ib.

the voltage given in the question is to throw you off,you dont need it.

Basically if Ie=Ib+Ic then Ib =Ie-Ic

So Ib =50.01-.50

Ib=49.51mA

DublinDilbert

Your figures don't look correct, you'd damage the base if you pump that amount of current in or out of the base.

Normally the base current will be much much smaller than the collector/emitter current. Intact the base current will be the collector current divided by hfe...

FarmerGreen

2N3055 spec http://www.onsemi.com/pub_link/Collateral/2N3055-D.PDF

Ic max = 15A
Ib max = 7A

If you are using the transistor as a switch, its normal to have excess base current to ensure saturation i.e. fully on.

.G.

I did phase 4 in January and thats what we used.The figures are not normally given much consideration when they make up these questions to be honest.Whether they are realistic or not is besides the point though they generally try to make the figures seem sensible

The question is designed to see if the student can

A: find the correct formula
B: transform the formula correctly
C: put the numbers in correctly and get the answer out correctly relative to the figures provided

The only formulas on the phase 4 formula sheet for transistors are Ie=Ic+Ib or hfe=Ic/Ib.

We aren't give hfe or Ib so the other formula is the only one that can be used to find Ib

danjo

hfe is not relevant when transistor is in saturation.

dingding

Also think of kirchoffs law where the sum of the currents into a point is equal to the sum of the currents out of the point.