Question

A transistor is said to be useful to be configured as an amplifier when its β is
1. Less than 0
2. Between 0 and 1
3. Between 1 and 50
4. > 50

Answer 1

Correct Answer - Option 4 : > 50

For the current gain of the common emitter amplifier to be large the value of β needs to be very high. 

In such cases, we can say that it works as a current amplifier, i.e. a small base current controls a larger (typically 100 times) current in the collector. 

The comparison of the various configuration of Amplifiers is as shown:

Parameter	Common-Base	Common-Emitter	Common-Collector	CE (Darlington)
Input Current	IE	IB	IB	IB
Output Current	IC	IC	IE	IC
Current Gain	\({\alpha _{dc}} = \frac{{{I_C}}}{{{I_E}}}\)	\({β _{dc}} = \frac{{{I_C}}}{{{I_B}}}\)	\(\gamma = \frac{{{I_E}}}{{{I_B}}} = \left( {1 + {β _{dc}}} \right)\)	\({β _{dc}} = {β _1}{β _2}\)
Voltage Gain	Medium	Medium	Less Than 1	Medium