DIGITAL CONDENSER MICROPHONE INCLUDING A PREPROCESSING AMPLIFIER HAVING VARIABLE INPUT IMPEDANCE, AND METHOD FOR ADJUSTING THE VARIABLE INPUT IMPEDANCE OF THE PREPROCESSING AMPLIFIER

摘要

Provided are a digital condenser microphone including a preprocessing amplifier having variable input impedance, and to a method for adjusting the variable input impedance of the preprocessing amplifier. The preprocessing amplifier of the digital condenser microphone according to the present invention comprises: a bias terminal for applying a bias voltage to an input signal when the input signal is outputted from a microphone condenser; an impedance unit including at least one variable input impedance device to which a bias voltage is applied through the bias terminal; an operational amplifier for receiving the input signal, converting the latter into an output signal, and outputting the output signal; and a control block for determining whether or not the DC voltage level of the output signal outputted from the operational amplifier has reached a reference value, and adjusting the total impedance value of said impedance unit on the basis of the result of said determination.