Dictionary:AGC time constant
The time required for the voltage of a system under automatic gain control to return to 63 % (or 1–1/e) of its final steady-state value after a sudden change in input level. If the change is an increase, the constant is called attack time; if a decrease, release time (which may be different from attack time). AGC time ‘‘constants’’ sometimes depend on factors such as signal level and the magnitude of the change. AGC characteristics are usually specified in dB/s. See Figure A-25.