ELECTRONICS 1
(ELC152X/ELC150X)
BIPOLAR JUNCTION TRANSISTORS
Tutorial 1
Feb-24
1
Question 1
a.
What are the bias conditions of the base-emitter and base-collector junction for a transistor to operate as an
amplifier?
b.
Which one is the largest of the three transistor currents?
c.
Is the base current smallest or larger than the emitter current?
d.
Is the base region much thinner or much wider than the collector and emitter regions?
e.
Define 𝛽𝛽𝐷𝐷𝐷𝐷 and 𝛼𝛼𝐷𝐷𝐷𝐷 . What if ℎ𝑓𝑓𝑓𝑓 ?
f.
g.
What are the two variables plotted on a collector characteristic curve?
Does 𝛽𝛽𝐷𝐷𝐷𝐷 increase or decrease with temperature?
h.
What bias conditions must exist for a transistor to operate as an amplifier?
i.
Which junctions are forward-biased in the saturation region?
j.
Which junctions are reverse-biased in a cutoff region?
Question 2
Consider the given figure with 𝑅𝑅𝐵𝐵 = 3.9 𝑘𝑘Ω,
𝑉𝑉𝐵𝐵𝐵𝐵 = 5 𝑉𝑉, 𝑅𝑅𝐶𝐶 = 180 Ω, 𝑉𝑉𝐶𝐶𝐶𝐶 = 155𝑉𝑉, 𝛽𝛽𝐷𝐷𝐷𝐷 = 50,
Determine :
a) 𝐼𝐼𝐵𝐵 , 𝐼𝐼𝐶𝐶 , 𝐼𝐼𝐸𝐸
b) 𝑉𝑉𝐶𝐶𝐶𝐶
c) 𝑉𝑉𝐶𝐶𝐶𝐶
Fig 2.1
Question 3
Given figure 3.2, find
𝐼𝐼𝐵𝐵 , 𝐼𝐼𝐸𝐸 , 𝑎𝑎𝑎𝑎𝑎𝑎 𝐼𝐼𝐶𝐶 , 𝑤𝑤𝑤𝑤𝑤𝑤𝑤 α𝐷𝐷𝐷𝐷 = 0.98
Fig 3.1
Question 4
a) Given the transistor in fig 3.1, calculate
𝐼𝐼𝐶𝐶 𝑠𝑠𝑠𝑠𝑠𝑠 , 𝐼𝐼𝐵𝐵 𝑎𝑎𝑎𝑎𝑎𝑎 𝐼𝐼𝐶𝐶 and determine whether the
transistor is in saturation, assuming
𝑉𝑉𝐶𝐶𝐶𝐶 𝑠𝑠𝑠𝑠𝑠𝑠 = 0.2 𝑉𝑉
b) Repeat a) given the following values:
𝛽𝛽𝐷𝐷𝐷𝐷 = 125, 𝑉𝑉𝐵𝐵𝐵𝐵 = 1.5𝑉𝑉, 𝑅𝑅𝐵𝐵 = 6.8𝐾𝐾Ω,
𝑅𝑅𝐶𝐶 = 180 Ω, 𝑎𝑎𝑎𝑎𝑎𝑎 𝑉𝑉𝐶𝐶𝐶𝐶 = 12𝑉𝑉
Fig 4.1
Question 5
a) Determine the terminal voltages of the
transistor in figure 5.1 with respect to ground
and 𝑉𝑉𝐶𝐶𝐶𝐶 , 𝑉𝑉𝐵𝐵𝐸𝐸 𝑎𝑎𝑎𝑎𝑎𝑎 𝑉𝑉𝐶𝐶𝐵𝐵
b) The power dissipation derating factor for a
certain transistor is 1𝑚𝑚𝑚𝑚/°𝐶𝐶, 𝑃𝑃𝐷𝐷 𝑚𝑚𝑚𝑚𝑚𝑚 =
0.5𝑊𝑊 𝑎𝑎𝑎𝑎 25°𝐶𝐶. What is 𝑃𝑃𝐷𝐷 𝑚𝑚𝑚𝑚𝑚𝑚 at 100°𝐶𝐶?
Fig 5.1