Transistors

Question 1

What is a transistor action?

Answer 1

ability of the base-emitter current to modulate the collector-emitter current

ex. V.be forces emitter current to be 1000 microamp but the collector takes 990 microamp leaving i.b+10microamp for the same V.be

Question 2

Transistor in the sense of silicon blocks?

Answer 2

silicon npn block representing the transistor as two super imposed pn junction diodes using the same p block which is very thin

Question 3

Base collector diode conducts what?

Answer 3

I.s

Question 4

equation for current equation in transistors?

Answer 4

i.d=i.s[e^x-1] where x=eV/kT

Question 5

What attracts electrons in the transistor symbol?

Answer 5

the collector E field, the electrons from the emitter n block

Question 6

Do you know what an open collector circuit is?

Answer 6

All points in a transistor would have the same current.

Question 7

What is the key to Transistor action?

Answer 7

V.be is constant? the emitter current does not change when E collects electrons for the collector, because the emitter is unaware of the collector’s action.

Question 8

What is alpha?

Answer 8

the fraction of emitter current collected.

i. c=alpha * i.e
i. b=(1-alpha)*i.e
i. c+i.b=i.e

Question 9

If there is an increase in i.c, what will happen?

Answer 9

nothing. maximum collected is alpha*i.e, i.c becomes a constant in the current generator

Question 10

what is Beta?

Answer 10

ic/ib

Beta is base-to-collector current gain

Question 11

What is a load line?

Answer 11

load line is used in graphical analysis of nonlinear electronic circuits, representing the constraint other parts of the circuit place on a non-linear device, like a diode or transistor.

The points where the characteristic curve and the load line intersect are the possible operating point(s) (Q points) of the circuit; at these points the current and voltage parameters of both parts of the circuit match.

Question 12

What do you do if your transistor enters the saturated region?

Answer 12

Use a shottky clamped transistor, an npn transistor with a barrier diode connected from base to collector to limit x if a transistor tries to move in the saturated region

although the shottky is on, the base-collector pn junction is still off.

clamp the transistor out of saturation by diverting current from the base to the collector

Question 13

Why are we concerned about diverting current from the base to the collector?

Answer 13

speed of operation. a saturated transsitor takes more time to turn off.