The FAB4300 Module is a Unity Buffer Amplifier Module, utilizing either a PDIP8 chip, or a Discrete OpAmp.

It has a single-ended input, and a single-ended output. The output of the OpAmp is connected back to it’s inverting input (IN-), while the input signal is applied to the non-inverting input (IN+).  The output of the OpAmp basically follows whatever is the input signal applied to IN+, thus  it’s named a voltage follower.

While the FAB4300 does not offer any amplification to the input signal, it serves a very important function. The input impedance of the FAB4300 Module is very high, meaning that the FAB4300 does not load down the signal source. At the same token, the output impedance of the FAB4300 Module is very low and thus it can drive loads very efficiently without any apparent loss in signal. You can say the FAB4300 acts like an impedance bridging circuit.

One practical application of the FAB4300 is in Active DI circuits (for electric guitars and bass guitars). You can connect the input of the FAB4300 to a high impedance source (like the magnetic pickup of an electric guitar), and then connect the output of the FAB4300 to your typical mic/line amplifier module.  You can use a JFET-type OpAmp for such purpose, like an OPA134 or equivalent. I’d strongly recommend using an OpAmp that is unity stable (i.e. Gain=1).



Update 4/29/13

I added on the board the option of using a SOIC-8 surface mount chip. The new board design is displayed below.

The prototype board has also been sent out for manufacturing.





3D Rendering