An amplifier has a 40 dB gain. Its gain may change by 100%. Then the v...
Understanding Gain in dB
The gain of an amplifier is given as 40 dB. To convert this to a linear scale, we use the formula:
- Gain (linear) = 10^(Gain(dB)/10)
- Gain (linear) = 10^(40/10) = 10^4 = 10,000
Effect of Gain Change
If the gain can change by 100%, the new gain could either double (gain increases) or halve (gain decreases). Therefore:
- Maximum Gain = 2 * 10,000 = 20,000
- Minimum Gain = 10,000 / 2 = 5,000
Feedback Factor Calculation
The feedback factor (β) can be determined using the formula:
- β = 1 / (Gain + 1)
Using both maximum and minimum gain values:
1. For Maximum Gain (20,000):
- β_max = 1 / (20,000 + 1) ≈ 0.00005
2. For Minimum Gain (5,000):
- β_min = 1 / (5,000 + 1) ≈ 0.0002
Choosing the Feedback Factor
Among the options given:
- (a) β = 0.1
- (b) β = 10
- (c) β = 0.09
- (d) β = 0.001
The calculated values of β for the maximum and minimum gain indicate that the feedback factor is much smaller than 0.1 and 0.09, and closer to 0.001.
Conclusion
Thus, the most suitable value for the feedback factor β is:
- Answer: (d) β = 0.001