Filters

The Low Pass filter uses passive components and is designed with a cutoff frequency of 100 KHz.  The filter is a 5 pole lowpass filter designed according to guidlines in the book "The Art of Electronics", by Horowitz and Hill, published in 1980.  Filter design is discussed in one of the extensive appendices.  This is a very popular book, and your local library should be able to help. Here is the circuit diagram: Low Pass Filter (Image, 29 Kb).

The 60 Hertz Notch Filter is easy to build using off-the-shelf components.  The filter uses the TL-082 operational amplifier as the active element.  The TL-082 is available from Radio Shack as part #276-1715.  The circuit was built per the  National Semiconductor Linear Brief LB-5.  If you have Adobe Acrobat installed on your computer, you can view the circuit here: National Semiconductor LB-5. Otherwise, look in the National Semiconductor book "Linear Applications Handbook", 1994, Page 1149.

I had access to a precision LCR test meter during construction, and carefully matched the components.... as discussed briefly in the text of the Linear Brief.  The Notch Filter is operated from split +/- 5 volt supplies. It is contained inside an aluminum box.  The input and output connectors are BNC style.