Peak detectors have low threshold, fast attack, slow decay and may be linear, quadratic or logarithmic.
The input may be an RF carrier or a nanosecond pulse. Each of these metrics must have a spec as each solution may be different. Some with perpetual S&H, others with decay on pulse etc.
Long long ago IBM invented a way of define problems called HIPO.
Hierarchical, Input, Process, Output
YOu may also have a process with just a simple proportional gain control with noise rejection that needs to be defined. You may also have an nonlinear response to big signals, dropouts and small signals. YOu may want to compress noise spikes.
INPUTS
Input range [V]
frequency range [Hz]
Rise time
Decay time
PROCESS
OUTPUT
Precision rectifiers for audio range use a diode feedback and Op AMps.
RF may use Pin diodes.