Determine Vo for [i] Vbb=0, [ii]Vbb=1V, and [iii] Vbb=2V

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Determine Vo for [i] Vbb=0, [ii]Vbb=1V, and [iii] Vbb=2V Beta = 75

Beta = ic/ ib

Where ic and ib are currents through the collector and base of the transistor.

[i] Vbb=0

ib = (Vbb - Vbe) / Rb = 0; Transistor is off.

Vo = Vcc- Ic Rc = 5 V; since Ic = 0, as Ib = 0

Ic is the current trough Rc, and should not be confused with ic. In the second case, where we write the KCL, it will be more clear. It is basically the sum of currnts ic and IL ( the current through resistor Rl)

Vo = Vcc= 5 V.

[ii]Vbb=1V

ic = Beta * Ib = Beta * [(Vbb - Vbe) / Rb];

= 75 * [(1 - 0.7) / 50k ] --------------assuming vbe = 0.7 V

ic= 0.45 mA = 450 uA

Applying KCL at the output node.

(Vcc - Vo)/Rc = ic + Vo/RL
Vcc/Rc - Vo/ Rc = ic + Vo/ RL ; Vo [ 1/RL + 1/ Rc] = [Vcc/Rc - ic]

Vo = (5/5k - 0.45m) / (10k/3) = 1.65 u V. - please check the numbers.!

[ii]Vbb=2V

Just the same as above except, replace Vbb = 2V instead of 1 V.

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