Integrated Circuits and Systems group, IIT Madras

Opamp based universal filter

  • The circuit below can have inputs Vi1,R, Vi1,C, Vi2,R, Vi2,C, Vi3,R and output V1, V2, V3. Determine the transfer functions for all input-output combinations.
  • Which components do the resonant frequency and the quality factor depend on?
  • Which components do the zeros depend on?

  • Design a bandpass filter (with V1 as output) for a resonant frequency of 3kHz and a quality factor of 5. Where will you apply the input? (Omit all unnecessary components from the circuit) Verify its operation.
  • While keeping the circuit the same, can you take the output from a different point to realize a lowpass filter? Verify it.
  • What is the minimum modification required to get a lowpass filter output at V1? Verify it.
  • What is the minimum modification required to get a highpass filter output at V1? Verify it.