In a passive mixer, switches and a capacitance are shared between bootstrapped mixing transistors, reducing the number of components required as compared to prior art bootstrap designs. Shared bootstrap circuits operate in an interleaved fashion between I and Q mixer circuits, at twice the LO frequency. That is, the shared bootstrap circuits in each I mixer circuit charge their capacitors in a first half-period of a clock, and connect the shared capacitor to the gate of an enabled mixing transistor in the second half-period. The shared bootstrap circuits in the Q mixer circuit charge their capacitors in the second half-period, and connect the shared capacitor to the gate of an enabled mixing transistor in the first half-period. One of two mixing transistors connected to each shared bootstrap circuit is alternately enabled during the clock signal half-periods that the shared bootstrap circuit is not charging its capacitor.