Your input signal is a mono audio signal that is the output of an electret conde
ID: 1809858 • Letter: Y
Question
Your input signal is a mono audio signal that is the output of an electret condenser microphone. An
electret condenser microphone output always includes a DC offset in addition to the signal itself.
Suppose that this microphone outputs a signal with a voltage swing of 200 mVpp plus a DC offset of 5
V. This microphone output signal needs to be changed before being input to a sensitive audio
circuit. Specifically, it needs to be inverted, amplified, and the DC offset needs to be
removed. Design and build a circuit that will cancel out the DC offset and achieve
maximum signal amplification without exceeding the 20 Vpp input limit of the audio
equipment.
Model the output of this microphone as
0.1 sin(2?
Explanation / Answer
DC offset is usually undesirable when it causes saturation or change in the operating point of an amplifier. An electrical DC bias will not pass through a transformer; thus a simple isolation transformer can be used to block or remove it, leaving only the AC component on the other side. In signal processing terms, DC offset can be reduced in real-time by a high-pass filter. When one already has the entire waveform, subtracting the mean amplitude from each sample will remove the offset. Often, very low frequencies are called "slowly changing DC" or "baseline wander"
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