The engineering of tin halide perovskites has led to the development of p-type transistors with field-effect mobilities of over 70 cm2 V-1 s-1. However, due to their background hole doping, these perovskites are not suitable for n-type transistors. Ambipolar lead halide perovskites are potential candidates, but their defective nature limits electron mobilities to around 3-4 cm2 V-1 s-1, which makes the development of all-perovskite logic circuits challenging. Here we report formamidinium lead iodide perovskite n-type transistors with field-effect mobilities of up to 33 cm2 V-1 s-1 measured in continuous bias mode. This is achieved through strain relaxation of the perovskite lattice using a methylammonium chloride additive, followed by suppression of undercoordinated lead through tetramethylammonium fluoride multidentate anchoring. Our approach stabilizes the alpha phase, balances strain and improves surface morphology, crystallinity and orientation. It also enables low-defect perovskite-dielectric interfaces. We use the transistors to fabricate unipolar inverters and eleven-stage ring oscillators.|The use of additives in the fabrication of solution-processed n-type perovskite transistors alleviates lattice strain and suppresses undercoordinated lead, boosting the charge transport properties of the devices and making them suitable for use in complementary circuit applications.