Deep Dive: E7B09
The correct answer is D: Input and output signals in-phase. What is characteristic of an emitter follower (or common collector) amplifier is that input and output signals are in-phase. Emitter followers don't invert the signal. For amateur radio operators, this is important for amplifier knowledge. Understanding this helps when working with amplifiers.
Why Other Answers Are Wrong
Option A: Incorrect. Low input impedance and phase inversion isn't correct - emitter follower has high input impedance and no phase inversion. Low impedance/phase inversion isn't correct. Option B: Incorrect. Differential inputs and single output isn't emitter follower - emitter follower has input and output in-phase. Differential inputs isn't the characteristic. Option C: Incorrect. Acts as OR circuit if one input grounded isn't emitter follower - emitter follower has input and output in-phase. OR circuit isn't the characteristic.
Exam Tip
Emitter follower characteristic = input and output signals in-phase. Think 'E'mitter 'F'ollower = 'E'choes 'F'ollows (in-phase, no inversion). Emitter followers don't invert the signal. Not low impedance/phase inversion, not differential inputs, not OR circuit - just in-phase signals.
Memory Aid
Emitter follower characteristic = input and output signals in-phase. Think 'E'mitter 'F'ollower = 'I'n-phase. Emitter followers don't invert the signal. Important for amplifier knowledge.
Real-World Example
An emitter follower (or common collector) amplifier: A characteristic is that input and output signals are in-phase. The output follows the input without phase inversion. This is the characteristic - input and output in-phase.
Source & Coverage
Question Pool: 2024-2028 Question Pool
Subelement: E7B
Reference: 2024-2028 Question Pool · E7 - Practical Circuits
Key Concepts
Verified Content
Question from the official FCC Extra Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the E7B topic.