Design and simulate ultra-low power microphone preamp into MCU ADC

Use analog design, active filter design, digital design, power supply design, Orcad 16.3, PSpice to design and simulate 1) Ultra-low power variable microphone preamp and low-pass nyquist filter 1) Dual-rail cascaded LDO power supply with virtual ground. Audio signal feeds into MCU ADC with USB port and capacitive touch sensor. Use of other tools such as Altium Designer may be possible.