I am designing an audio circuit that operates at 5 volts. Is it reasonable to buy a wall adapter that outputs 5V, or should I buy a wall adapter that outputs a higher voltage and step the voltage down at the PCB with a linear or switching regulator?
The audio circuit operates at 5V to achieve a volume level. The audio signal source will come from a microcontroller regulated at 3.3V.
The wall adapter I am considering is medical grade; part # MDS-030AAC05 AB.
Best Answer
Yes you can, match the voltage of the rail and make sure that the total current of the circuit (and IC's) you are using is less than the current rating on the supply.
Realize each voltage source carries noise. Be aware that for analog circuits the PSRR rating will tell you how much noise will transfer from the power supply rails to your signal (this number is usually well over 80dB).
If you have a direct pathway to the rail (like a pull up resistor or a DC path to the power rail) then this could inject noise in directly from the rail.
Measure the noise on the power supply with a volt meter set on AC mode, this will tell you the RMS value of the ripple or noise, if its acceptable for your application then you can use it. If the noise is to high for your application, find a new supply, use an LC filter or a precision linear regulator.