Low noise microphone preamplifier

摘要

An integrated circuit preamplifier amplifies an input signal comprising first and second differential input signals to provide an amplified output signal comprising first and second differential output signals. A biasing circuit of the preamplifier provides a bias current. An open-loop differential amplifier of the preamplifier is coupled to the biasing circuit. The differential amplifier includes a differential amplifier pair having first and second differential amplifying transistors, which are coupled at respective gate terminals to the first and second differential input signals. Each of the amplifying transistors are coupled in open-loop configuration at a drain terminal to a respective load resistor coupled to ground, and the source terminals of the amplifying transistors are coupled together to receive the bias current. The first and second differential output signals are formed across the respective first and second load resistors.