The primary difference between a log detector and a logarithmic (log) amplifier lies in the way the detector and amplifier processes the signal and the specific applications. A log amplifier provides an output that is proportional to the logarithm of the input signal's amplitude. The log amplifier is designed to handle a wide dynamic range of input signals by compressing them logarithmically. Log amplifiers are commonly used in applications where signal compression is needed, such as in RF signal processing, audio level compression, and true RMS detection. A log detector, also known as a demodulating log amplifier, provides an output that is proportional to the logarithm of the envelope of the input signal. A log detector essentially demodulates the signal and then applies a logarithmic function to the envelope. A log detector generally used to measure signal strength over a wide dynamic range.

In summary, while both devices perform logarithmic functions, a log amplifier works directly on the input signal's amplitude, whereas a log detector focuses on the envelope of the input RF signal.

The following paragraphs of this article shows how a Logarithmic detector can be used at the receive side of the signal chain to achieve better performance in terms of input sensitivity, dynamic range, noise and gain control as compared multi-gain stage traditional op-amps configuration in various ultrasonic sensing applications.