Updated 9 nov 2012
I did a schematic and PCB layout job for my brother Bertrik Sikken. I used Cadsoft Eagle to design the schematic and PCB layout. This amplifier board is placed with header connectors on top of a LPC-P2148 microprocessor board from Olimex. Together these boards form a battery powered stereo ultrasonic recorder that stores the ultrasonic sound from bats directly to SD card without converting it first to audible signal. The battery and the microphones are connected to the microcontroller through the amplifier board. They will be used in scientific research and will be used to investigate activity of bat colonies and in which direction they travel to. The design of V1 was recenly verified and we found oscillation and a noisy signal. I debugged the board and the main problem was that the output signal is capacitively coupled to the sensitive input signal and also bad grounding. In version 2 of PCB the layout has very much improved. The sensitive input signal is now completely separated from the output, the input connector is now at 1/3rd distance w.r.t. V1, the grounding is improved very much, and the power supply and reference voltages are decoupled better, so I expect a lot from this new design.
Below is version 2 of the PCB. It was ordered from Iteadstudio for the incredible low price of 22 dollar for 10pcs of 2 layer boards. The dimension in approximately 4 by 7 cm. Most parts were ordered from Dick Best and you can find the BOM below.
Version 1Schematic in PDF, Schematic in EAGLE, Layout in PDF, Layout in EAGLE
Version 2 Schematic in PDF, Schematic in EAGLE, Layout top in PDF, Layout bot in PDF, Layout in EAGLE, Gerber files, BOM