Question 5
- State four advantages of the transistor over the thermionic valve.
- Draw and label the circuit symbol of a p-channel Field Effect Transistor.
- A transistor amplifier connected in common emitter mode has a collector load resistance of 2000Ω. If the short-circuit current gain (hfe) of the transistor is 100 and its input resistance (Rin) is 1000Ω. Calculate the voltage gain.
Observation
The expected answers were;
(a) Advantages of Transistor over Thermionic Valve
- Higher efficiencies.
- Transistors consume less power than thermionic valves.
- Transistors are smaller in size compared to thermionic valves.
- Transistors require less working voltage.
- Lower cost
- Fast switching
- Severaltransistors can be integrated on a single chip
P-channel FET symbol
(c) hfe = 100
Rin = 1,000 Ω
RL = 2,000 Ω
- Voltage gain (Av)
Only a few candidates could state the advantages of transistor over vacuum tube valve.
Generally, candidates’ responses to question were poor.