Question 3
(a)State three advantages of a transistor over a triode.
(b)State one reason why a triode is regarded as voltage-controlled device.
(c)Draw and label the circuit symbol of a pentode valve.
OBSERVATION
The Chief Examiner reported that question 3 ‘s first two sub-questions are simple recall questions; one concerning the advantages of the transistor over the vacuum tube triode, A few candidates recalled the fact that the triode is a voltage-controlled device on account of the functioning of its control grid, but none could explain exactly why. Only a few candidates could give a sketch of the pentode, and many of those who did, could not correctly locate the five electrodes.
<<<<<<< HEAD
The expected responses were:
(a) Advantages of a transistor over a triode
=======The expected responses were:
(a)Advantages of a transistor over a triode
>>>>>>> 1639acb3c8d78353a269a20c9972528635165226- Small in size (compactness)
- Cheaper
- Less power consumption
- Higher efficiency(faster in operation)
- Ruggedness/Durability
- Tighter clearance
- Produces less heat
(b)Why a triode is regarded as a voltage-controlled device
- It has a very high input resistance/impedance.
- Input voltage controls the output current.
(c)Labelled diagram of the circuit symbol of a pentode valve
