Filtering Spurious Signals in a Wireless Transceiver

An electronic device may include wireless circuitry having a transformer with a primary coil and a secondary coil, a first series inductor coupled to the primary coil, a second series inductor coupled to the primary coil, and a filter inductor inductively coupled to the first and second series inductors and operable to produce a first filter response when the wireless circuitry is operable in a first mode and a second filter response when the wireless circuitry is operable in a second mode. The transformer can be coupled to another filter inductor. The transformer can be coupled to an active circuit. The active circuit can include input transistors and cascode transistors. The cascode transistors can be coupled to resistors and/or capacitors that are selectively activated using associated filter switches.