9.2.4 Microphone Pre-Amplifier

Figure 60. Low-Power Microphone Pre-Amplifier

Figure 60 shows an example circuit of the audio pre-amplifier application using OPA2834. The excellent distortion performance and the ultra-low quiescent current, make OPA2834 a very attractive solution for the portable and handheld audio instruments. Figure 60 circuit is a bandpass filter with frequency cutoff at 5 Hz and 180 kHz. The OPA2834 is connected to a positive 3.3 V and a negative 1.8 V supply. the primary reason for the skew in the power supply is to enable the maximum dynamic range possible to the user. The V_ICR of OPA2834 mentioned in Electrical Characteristics: 3V to 5V is 1.1 V from the positive rail. Thus having a skewed power supply like in Figure 60 gives a common-mode input range from -2 V up to 2.2 V.

Figure 61. Frequency Response of Microphone Pre-Amplifier