Low-Pass Filter for an Electret Condenser Microphone

This article is devoted to the design of a low-pass filter for an electret condenser microphone in an electronic stethoscope. A filter with replacement of inductors by an active circuit based on operational amplifiers with a bandwidth of 1 kHz was chosen as a low-pass filter. The bandwidth ripple of the device is 1.2 dB and the stopband attenuation is 76.87 dB. The stability of the frequency response to changes in the nominal values of the elements is analyzed, nonlinear distortions and noise characteristics are considered. The result is approved by simulation using CAD Micro-Cap 12.