6.2.4 Active Filters

Chapter 6.2.4 Active Filters

Physics Lecture Notes – Phys 395 Electronics Book
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Physics Lecture Notes – Phys 395 Electronics Book

  • CHAPTER 6. OPERATIONAL AMPLIFIERS113ΗA0G= −−−1RCωωωcωIFigure 6.12: Integration circuit frequency response.The frequency response is shown in figure 6.12.We can combine the above inverting, summing, offset, differentiation and integrationcircuits to build an analog computer that can solve differential equations. However, today,the differentiators and integrators are mainly used to condition signals.6.2.4Active FiltersFilters often contain embedded amplifiers between passive-filter stages as shown in fig-ure 6.13.Figure 6.13: Buffer amplifier as part of active filter.These filters have a limited performance since the poles are still real and hence the kneesare not sharp. For example, a three stage high-pass filter with buffer amplifiers has a transferfunctionG(jω)=jω/ωc1+ jω/ωcjω/ωc1+ jω/ωcjω/ωc1+ jω/ωc=−j(ω/ωc)3(1 + jω/ωc)3,(6.26)