A novel second-order canonical RC-active realization of high-pass notch filter

A high-pass notch filter with variable gain greater than unity is realized using a differential amplifier and only two capacitors that can be equal. The transmission zero and pole frequency are completely independent of the amplifier dc gain. Design formulas, sensitivity analysis, and measure and trim tuning process are presented. An example of a 60-Hz rejection filter is discussed, the response of which is within the required specifications even with a 5-percent capacitance variation. Two modifications of the original structure can be used to realize the same filter, extending the available range of the gain to cover all requirements.