Passive filters

• No power supplies and no active components (transistors, diodes, ...)
• Gain is always ≤ 1
• Output load becomes part of the circuit

• First order low-pass filter

               Gain:

                                                                                   Corner frequency:

                                                                                    Rolloff: 20 dB/decade (for w >> w_c)

• Second order low-pass filter

     Gain:

                                                                                    Rolloff: 40 dB/decade (for w >> w_c)

For steeper rolloff, n filter stages can be connected in cascade

• First order high-pass filter

     Gain: