This circuit draws very little power, less than 5 mA with a single 6-V power supply. making it ideal for portable battery-operated equipment. The small size and low power consumption belie the 90-dB dynamic range and 10.5-I`V sensitivity. De output voltage proportional to the log10 of the input signal level. Thus, a standard 0 -5 voltmeter can be linearly calibrated in decibels over a single 80-dB range.
The circuit is within 1.5-dB tolerance over the 80-dB range for audio frequencies from 100Hz to 10kHz. Higher audio levels can be measured by placing an attenuator ahead of the input capacitor.