CHAPTE R 7 Highpass Filters Steve Winder I don't use a real high-pass filter every year, but I do use some audio coupling capacitors, and I do use sample-and-difference circuits in my testing. And that's a form of high-pass filter, so we will explain that. Because, as Steve Winder points out here, it's important to use a good "poly" cap, either polystyrene or polypropylene, not polyester. /rap In This Chapter This chapter describes how to design an analog active or passive highpass filter with