Filters and Amplifiers

Here is a listing of some experiments into basic active and passive filters along with the basic amplifiers formed from op amps. For the most part what these amplifiers do is pretty self explanatory. The reason they work was not investigated at this time as it was the first exposure to them really. Most values for capacitors was pF to nF range, with most in the low nF range and resistors in the low to mid KΩ range. Some important aspects to note are the gain bandwidth product of the amplifier. This helps in determining when the gain of the amp will drop off and the signal may get distorted. Also, keeping the input and output signal within the proper voltage ranges to prevent clipping is important.

Analog filters were mentioned in class before and used briefly in CPEG222 without much explanation. Here I test out some basic first order high pass and low pass filters. In the end I realized that they are ok for quick builds but they are not optimal for when you need a reliable circuit because of component mismatch. This is why people are moving to digital filters which will perform how you program them to perform. Also, at the end is listed some other information on better analog filter topologies.

Notice the phase of the signal.

Notice the phase of the signal.

Notice the phase of the signal.

The previous filters are all very simple passive or first order active. Much better analog filter designs are avaliable. One such filter type is the Butterworth Filter which has both an analog and digital realization. The Sallen-Key topology is a common analog filter realization used in CPEG222 for the filter design.