This Tiny Microphone Preamplifier is an excellent choice for noisy environments due to its high common mode rejection and excellent power-supply rejection. It operates from a single +2.4V to +5.5V supply. It is based on the MAX4468 IC from Maxim Integrated which is a low-cost micropower microphone preamplifier.
Most microphone preamplifiers are intended only for voice signals but this one can be used for full range audio due to its excellent Gain Bandwidth Product. The circuit is optimized to be used with an electret microphone-capsule but you can easily convert it to be used with any other type of microphone. For professional results, build this circuit and use a high quality electret capsule.
The circuit provides microphone bias and the MAX4468 has the ability to turn off the bias to the microphone when the device is in shutdown. In shutdown, the amplifiers’ supply current is reduced to 5nA and the bias current to the external microphone is cut off for ultimate power savings.
The circuit is based on Maxim’s datasheet. We have just add a trimmer potentiometer for gain adjust and a simple switch to turn – off or on the preamplifier. We have connected an external pull-down resistor to the SHDN pin and you will notice that when the device is in shutdown mode this resistor consumes much more current than the IC itself.
Many people think that building manually a circuit which has only SMT components is a real nightmare! We don not think the same. Using the PCB provided here, we just believe that some special care is needed. Any hot-air soldering equipment and good magnifying lens will be much helpful.
Artwork by: A.G
Tiny Microphone Preamplifier Electronic Schematic and PCB Artwork