Analog Electronics - Study Mode

[#86] The cascade amplifier is a multistage configuration of
Correct Answer

(D) CE-CC
(H) CE-CC

Explanation

Solution: Explanation of each option: Option A: CC-CB is incorrect because this configuration consists of a common collector (CC) stage followed by a common base (CB) stage. While this can be used in some amplifiers, it is not a typical configuration for a cascade amplifier. Option B: CE-CB is incorrect because this configuration consists of a common emitter (CE) stage followed by a common base (CB) stage. While this may be used in certain applications, it is not the standard configuration for a cascade amplifier. Option C: CB-CC is incorrect because this configuration starts with a common base (CB) stage followed by a common collector (CC) stage. This is also not a common arrangement for cascade amplifiers. Option D: CE-CC is correct because the typical cascade amplifier configuration uses a common emitter (CE) stage followed by a common collector (CC) stage. The CE stage provides high voltage gain, while the CC stage provides current gain and impedance matching, making this a common choice for multistage amplifiers. Conclusion: The correct answer is Option D: CE-CC because this is the standard multistage configuration for cascade amplifiers.

[#87] An npn BJT has g m = 38 mA/v, C µ = 10 -14 F, C π = 4 × 10 -13 F and DC current gain β 0 = 90. For this transistor f T & f β are
Correct Answer

(B) f T = 1.47 x 10 10 Hz & f β = 1.64 x 10 8 Hz

[#88] Negative feedback in an amplifier
Correct Answer

(A) Reduces gain

Explanation

Solution: Option A: Reduces gain is correct because negative feedback in an amplifier reduces the overall gain of the system. This reduction in gain, however, leads to improved linearity, reduced distortion, and better stability in the amplifier's operation. Option B: Increase frequency & phase distortion is incorrect because negative feedback actually helps reduce both frequency and phase distortion. It enhances the fidelity of the amplifier by minimizing these distortions. Option C: Reduces bandwidth is incorrect because negative feedback typically increases the bandwidth of an amplifier. It makes the amplifier more stable across a wider range of frequencies. Option D: Increases noise is incorrect because negative feedback reduces the overall noise in an amplifier. By stabilizing the gain and reducing distortion, it typically lowers the noise figure of the amplifier. Conclusion: The correct answer is Option A: Reduces gain because negative feedback decreases the amplifier's gain but improves its overall performance in terms of linearity, stability, and distortion reduction.

[#89] In a Wien bridge oscillator, the positive feedback attenuation is
Correct Answer

(A) $$frac{1}{3}$$

[#90] Which one of the following multivibrators does not required input clock pulse or trigger?
Correct Answer

(C) Astable