IPS Engineering – electronics
Examples and exercises
DMN, 20150204
Give the conditions for the normal
operation of the transistor.
Kirchoff's definition diagram
a. Calculate the amplification factor.
b. Graphically determine the Q-point for
Ib = 20 µA and Rc = 2kΩ, U = 10 V
a. Give the base current in µA if ß = 200.
b. Determine the Q-points for
Rc = 500Ω, U = 5 V
a. Determine the amplification factor at Vs = 8 V
and Is = 2 mA and Is = 10 mA.
What do you notice?
b. The base is being driven with Ib = 10 µA.
Uce = 10 V. U = 20 V
Calculate the required collector resistance using
Kirchoff's circuit laws.
The following two graphs are of the same transistor:
Ube-Ib curve
a. Calculate the required base current using Kirchoff's circuit laws when:
U = 24 V, Uce = 3 V, Rc = 180 Ω
b. Calculate the exact base resistance when that base voltage source Uin = 5V.
c. Calculate the power developed in the transistor.
d. What is the minimum base current you need to drive the 180 Ω completely (saturation
area)?
The solution can be given graphically or by using the determination for ß.
We use quadrants 1 and 3 of the following transistor characteristic.
a. What is the approximate amplification factor at Uce = 5V?
b. If the base is driven with 2 mA, what is Ube??
c. If the base is driven with 2 mA and there is a power LED in the collector that uses 100mA,
in which state will the transistor then be?
d. If you want to dim the LED, up to which values must the base current then drop?
e. Calculate the dissipation in the transistor if the power LED continues to be connected with
100mA and the base current is 0.5 mA.