What is the gain-bandwidth of an operational amplifier?
The correct answer is B: The frequency at which the open-loop gain of the amplifier equals one. The gain-bandwidth product (or gain-bandwidth) of an operational amplifier is the frequency at which the open-loop gain equals one (unity gain frequency). This is a key specification that determines the op-amp's frequency response.
The gain-bandwidth product is constant for a given op-amp. As frequency increases, the open-loop gain decreases. At the gain-bandwidth frequency, the gain has dropped to 1 (0 dB). This frequency determines the maximum useful operating frequency of the op-amp. For example, if an op-amp has a gain-bandwidth of 1 MHz, and you configure it for a closed-loop gain of 10, the bandwidth will be approximately 100 kHz (1 MHz / 10 = 100 kHz). This relationship is fundamental to op-amp circuit design.
Exam Tip
Gain-bandwidth = Unity gain frequency. Remember: Gain-bandwidth is the frequency where open-loop gain equals one. It's constant for a given op-amp and determines frequency response limits.
Memory Aid
"**G**ain-**B**andwidth = **G**ain **O**ne **F**requency (think 'GB = GOF' = Gain One Frequency, unity gain)"
Real-World Application
You're designing an audio amplifier with an op-amp that has a gain-bandwidth product of 1 MHz. If you configure the op-amp for a gain of 20, the bandwidth will be approximately 50 kHz (1 MHz / 20). The gain-bandwidth product tells you the frequency limits of your amplifier design.
FCC Part 97.3Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. The gain-bandwidth isn't the maximum frequency for a filter circuit. It's the frequency where open-loop gain equals one.
Option C: Incorrect. The gain-bandwidth isn't the gain at a filter's cutoff frequency. It's a specific frequency where gain equals one.
Option D: Incorrect. The gain-bandwidth isn't related to offset voltage. Offset voltage is a DC error, while gain-bandwidth is a frequency response parameter.
题目解析
The correct answer is B: The frequency at which the open-loop gain of the amplifier equals one. The gain-bandwidth product (or gain-bandwidth) of an operational amplifier is the frequency at which the open-loop gain equals one (unity gain frequency). This is a key specification that determines the op-amp's frequency response. The gain-bandwidth product is constant for a given op-amp. As frequency increases, the open-loop gain decreases. At the gain-bandwidth frequency, the gain has dropped to 1 (0 dB). This frequency determines the maximum useful operating frequency of the op-amp. For example, if an op-amp has a gain-bandwidth of 1 MHz, and you configure it for a closed-loop gain of 10, the bandwidth will be approximately 100 kHz (1 MHz / 10 = 100 kHz). This relationship is fundamental to op-amp circuit design.
考试技巧
Gain-bandwidth = Unity gain frequency. Remember: Gain-bandwidth is the frequency where open-loop gain equals one. It's constant for a given op-amp and determines frequency response limits.
记忆口诀
**G**ain-**B**andwidth = **G**ain **O**ne **F**requency (think 'GB = GOF' = Gain One Frequency, unity gain)
实际应用示例
You're designing an audio amplifier with an op-amp that has a gain-bandwidth product of 1 MHz. If you configure the op-amp for a gain of 20, the bandwidth will be approximately 50 kHz (1 MHz / 20). The gain-bandwidth product tells you the frequency limits of your amplifier design.
错误选项分析
Option A: Incorrect. The gain-bandwidth isn't the maximum frequency for a filter circuit. It's the frequency where open-loop gain equals one. Option C: Incorrect. The gain-bandwidth isn't the gain at a filter's cutoff frequency. It's a specific frequency where gain equals one. Option D: Incorrect. The gain-bandwidth isn't related to offset voltage. Offset voltage is a DC error, while gain-bandwidth is a frequency response parameter.
知识点
Gain-bandwidth product, Unity gain frequency, Op-amp frequency response, Open-loop gain
Verified Content
Question from official FCC Extra Class question pool. Explanation reviewed by licensed amateur radio operators.