Consider a bipolar transistor with area A working under normal operating conditions.

$($a$)$ What are the bias directions $($forward or reverse$)$ of the BE and CB junction of a bipolar

transistor under normal operating conditions.

$($b$)$ Give magnitude and direction $($positive or negative$)$ of VBE, VCE, and VCB of a bipolar

transistor in the common emitter configuration under normal operating conditions.

Circle the correct answer$($s$).$

pnp transistor, common emitter configuration:

$(1)$ VBE $>0$ VBE $<0(2)$ VCE $>0$ VCE $<0$

$(3)$ VCB $>0$ VCB $<0(4)|$VBE$|>|$VCE$||$VBE$|<|$VCE$|$

npn transistor, common emitter configuration.

$(1)$ VBE $>0$ VBE $<0(2)$ VCE $>0$ VCE $<0$

$(3)$ VCB $>0$ VCB $<0(4)|$VBE$|>|$VCE$||$VBE$|<|$VCE$|$

Definition: VBE means the voltage between base $($B$)$ and emitter $($E$).$

$($c$)$ Explain why the base minority carrier concentration can be approximated by a

$$triangle$.$

$($d$)$ Plot the minority carrier concentration of a pnp bipolar transistor stored in the base on

a linear and logarithmic ordinate scale. Label the axes.

$($e$)$ Using the diffusion triangle, give or derive the formula for the minority charge in the

base.

$($f$)$ Determine the dependence $($linear$,$ quadratic, logarithmic, exponential, or other

dependence$)$ of the stored minority charge in the base on the $($i$)$ emitter current

$($ii$)$ base$-$emitter voltage. Give formulas and list all the assumptions and approximations

that you make.