Automatic level detector with wide input range - has rectifier working point stabilised by variable attenuation control loop

摘要

The automatic level detector for AC signal voltages is suitable for signals having a wide dynamic range, eg in the order of 50 dB. The amplified input (2) passes through a variable attenuator (3) adjusted in 10dB steps by logic signals from an analogue/digital converter (9), a further variable 10dB attenuator and a rectifier. The rectified signal is compared with an adjustable DC reference (8). The resulting error signal is fed to the variable attenuators which form part of a closed control loop so that the total attenuation in the signal path is such that the rectifier always operates over the same part of its characteristic. In this way the circuit is able to handle signals of wide dynamic range.