A detector that is sensitive to amplitude variation is called an amplitude detector or an envelope detector. It is commonly used to measure the varying amplitude of a signal or wave. The primary purpose of an amplitude detector is to extract the envelope or the low-frequency variations in the amplitude of a high-frequency carrier signal.
One common example of an amplitude detector is a diode-based envelope detector used in AM (amplitude modulation) receivers. In an AM signal, the information is encoded by varying the amplitude of a high-frequency carrier wave. The envelope detector extracts the varying amplitude component, which contains the modulating information, from the modulated carrier wave.
The diode-based envelope detector works by rectifying the incoming signal, which converts the negative half cycles of the wave to positive half cycles. Then, a low-pass filter is used to smooth the rectified signal, resulting in the detection of the envelope variations. The output of the envelope detector represents the original modulating signal or the baseband signal, which can be further processed for audio or data retrieval.
Other detectors, such as peak detectors and level detectors, can also measure amplitude variation but may serve different purposes. Peak detectors capture and hold the maximum amplitude value of a signal, while level detectors provide an indication or trigger based on a specific amplitude threshold.
Overall, an amplitude detector, such as an envelope detector, is designed to detect and measure variations in the amplitude of a signal or wave and is commonly used in applications such as AM radio, audio processing, and telecommunications.