This circuit can drive a small earphone speaker that requires up to 2 watts of power (e.g., 500 mA current into an 8 ohm speaker).
- It has unity gain in a non-inverting configuration (the speakers we work with only require about 1V maximum to achieve the desired sound levels).
- High-pass input stage with 1.26 Hz cutoff (basically a DC filter).
- Two BUF634 in parallel to provide up to 500 mA of current.
The board is 74mm x 48mm and the mounting holes, spaced 40mm x 40mm, are sized for a M3 screw. The board will fit in a Hammond enclosure that accomodates 75mm wide boards.
OSH Park will print and ship three of these boards for approximately $30.
Order the parts from the parts list. If you get a heat sink, Aavid Thermalloy 577202B00000G should fit nicely in the space allowed.
Solder all components. Be sure to attach heat sinks to the current buffers.
Wash the board with dH2O.
Previous iterations of the design had a high-pass filter on the output. However, we have modified the current iteration such that the high-pass filter is found on the input stage. This allows us to eliminate bulky components (required to handle the large current) that take up a lot of space.