Amplifier categories — match each stage type to its frequency range or operating class List I A. IF amplifier B. RF amplifier C. AF (audio-frequency) amplifier D. Class operation (e.g., Class A/B/C) List II 1. Amplifier frequencies in the range of about 100 kHz to 5 MHz 2. Current in the output flows only during a portion of the positive half of the input cycle 3. Amplifier frequencies in the range from near 0 Hz up to a few megahertz (low-to-mid frequencies) 4. Amplifier frequencies in the range of about 40 Hz to 15 kHz
-
AA-4, B-1, C-3, D-2
-
BA-3, B-1, C-4, D-2
-
CA-2, B-3, C-1, D-4
-
DA-1, B-2, C-3, D-4
Answer
Correct Answer: A-3, B-1, C-4, D-2
Explanation
Introduction / Context:Receiver and transmitter chains use AF, IF, and RF amplifiers at different stages. Separately, “class of operation” (A/B/C, etc.) describes the conduction angle of the active device. Matching these concepts helps relate block diagrams to device physics.
Given Data / Assumptions:
- Typical broadcast/communication frequency ranges.
- AF roughly spans human hearing (≈40 Hz to 15 kHz in many systems).
- IF stages commonly lie in the hundreds of kilohertz to a few megahertz, but the list item 3 summarizes a broad low-to-mid-frequency region that includes common IFs.
- Class operation is characterized by conduction angle (e.g., Class C conducts less than 180 degrees).
Concept / Approach:We map RF amplifiers to a representative 100 kHz–5 MHz band, AF amplifiers to 40 Hz–15 kHz, IF amplifiers to the broader low-to-mid band that includes common intermediate frequencies, and class operation to the definition involving partial-cycle conduction (typical of Class B/AB/C).
Step-by-Step Solution:
A (IF) → includes common IFs (e.g., 455 kHz, 10.7 MHz) → summarized under broad low-to-mid band → 3.B (RF) → representative lower-MHz region → 1.C (AF) → audio band → 4.D (Class operation) → partial-cycle conduction definition → 2.Verification / Alternative check:Standard superheterodyne receivers employ IFs in the hundreds of kHz to tens of MHz. AF power amplifiers target audio bandwidth. RF pre-selectors and power stages operate across designated RF bands.
Why Other Options Are Wrong:
- Swapping AF with RF bands misplaces the physical meaning of the stages.
- Linking “class operation” to a frequency band instead of conduction angle confuses biasing with spectrum.
Common Pitfalls:Treating list frequency bounds as universal—actual system IFs may be outside the example ranges; however, the relative ordering remains correct.
Final Answer:A-3, B-1, C-4, D-2