What best describes a pull-up or pull-down resistor?
The correct answer is B: A resistor connected to the positive or negative supply used to establish a voltage when an input or output is an open circuit. What best describes a pull-up or pull-down resistor is a resistor connected to the positive or negative supply used to establish a voltage when an input or output is an open circuit. Pull-up/pull-down resistors set default voltage levels. For amateur radio operators, this is important for digital circuits. Understanding this helps when designing digital circuits.
Exam Tip
Pull-up/pull-down resistor = resistor connected to supply to establish voltage when input/output is open. Think 'P'ull-'U'p/'P'ull-'D'own = 'P'rovides 'D'efault voltage. Pull-up/pull-down resistors set default voltage levels. Not keying circuit, not oscillator, not op-amp output - just establishes voltage when open.
Memory Aid
"Pull-up/pull-down resistor = resistor connected to supply to establish voltage when input/output is open. Think 'P'ull-'U'p/'P'ull-'D'own = 'D'efault voltage. Pull-up/pull-down resistors set default voltage levels. Important for digital circuits."
Real-World Application
A pull-up or pull-down resistor: It's a resistor connected to the positive or negative supply used to establish a voltage when an input or output is an open circuit. This ensures a defined logic level when the circuit is floating. This is the description - establishes voltage when open.
Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. Resistor in keying circuit to reduce key clicks isn't pull-up/pull-down - pull-up/pull-down establishes voltage when open. Keying circuit isn't the description.
Option C: Incorrect. Resistor ensuring oscillator frequency doesn't drift isn't pull-up/pull-down - pull-up/pull-down establishes voltage when open. Oscillator isn't the description.
Option D: Incorrect. Resistor connected to op-amp output preventing signals exceeding supply isn't pull-up/pull-down - pull-up/pull-down establishes voltage when open. Op-amp output isn't the description.
题目解析
The correct answer is B: A resistor connected to the positive or negative supply used to establish a voltage when an input or output is an open circuit. What best describes a pull-up or pull-down resistor is a resistor connected to the positive or negative supply used to establish a voltage when an input or output is an open circuit. Pull-up/pull-down resistors set default voltage levels. For amateur radio operators, this is important for digital circuits. Understanding this helps when designing digital circuits.
考试技巧
Pull-up/pull-down resistor = resistor connected to supply to establish voltage when input/output is open. Think 'P'ull-'U'p/'P'ull-'D'own = 'P'rovides 'D'efault voltage. Pull-up/pull-down resistors set default voltage levels. Not keying circuit, not oscillator, not op-amp output - just establishes voltage when open.
记忆口诀
Pull-up/pull-down resistor = resistor connected to supply to establish voltage when input/output is open. Think 'P'ull-'U'p/'P'ull-'D'own = 'D'efault voltage. Pull-up/pull-down resistors set default voltage levels. Important for digital circuits.
实际应用示例
A pull-up or pull-down resistor: It's a resistor connected to the positive or negative supply used to establish a voltage when an input or output is an open circuit. This ensures a defined logic level when the circuit is floating. This is the description - establishes voltage when open.
错误选项分析
Option A: Incorrect. Resistor in keying circuit to reduce key clicks isn't pull-up/pull-down - pull-up/pull-down establishes voltage when open. Keying circuit isn't the description. Option C: Incorrect. Resistor ensuring oscillator frequency doesn't drift isn't pull-up/pull-down - pull-up/pull-down establishes voltage when open. Oscillator isn't the description. Option D: Incorrect. Resistor connected to op-amp output preventing signals exceeding supply isn't pull-up/pull-down - pull-up/pull-down establishes voltage when open. Op-amp output isn't the description.
知识点
Pull-up or pull-down resistor, Resistor connected to supply, Establish voltage, Input or output open circuit
Verified Content
Question from official FCC Extra Class question pool. Explanation reviewed by licensed amateur radio operators.