A　low-power　multibit　delta–sigma　modulator　(DSM)　based　on　a　passive　and　unattenuated　summation　scheme　is　proposed.　The　summation　circuit　achieves　multiplication　of　the　voltage　signal　carried　on　the　summation　capacitor　through　a　bidirectional　sampling　technique,　thereby　compensating　for　the　inherent　attenuation　caused　by　passive　summation,　which　eliminates　the　need　for　an　active　operational　transconductance　amplifier　(OTA)　to　achieve　perfect　summation.　Here,　a　second-order　DSM　based　on　a　4-bit　first-order　passive　noise-shaping　(NS)　SAR　quantizer　is　employed　to　satisfy　the　SNDR　requirements　exceeding　100　dB,　which　validates　the　reliability　of　the　summation　scheme.　In　addition,　a　cascoded　floating　inverter　amplifier　(FIA)　is　used　as　the　core　OTA　to　further　improve　system　energy　efficiency.　Simulation　results　demonstrate　that　at　a　supply　voltage　of　1.2 V　and　a　bandwidth　of　20　kHz,　the　SNDR　reaches　102.62　dB,　power　consumption　is　only　148.32　μW,　and　the　Schreier　figure-of-merit　(FoM)　of　the　SNDR　is　183.92　dB.　The　results　demonstrate　that　the　proposed　DSM　has　considerable　potential　for　widespread　application　in　the　audio　domain.　©　2024　John　Wiley　&　Sons　Ltd.