Most general purpose processors (GPP) and application specific processors (ASP) use the floating-point arithmetic due to its wide and precise number system. However, the floating-point operations require complex processes such as alignment, normalization and rounding. To reduce the overhead, fused floating-point arithmetic units are introduced. In this dissertation, improved architectures for three fused floating-point arithmetic units are proposed: 1) Fused floating-point add-subtract unit, 2) Fused floating-point two-term dot product unit, and 3) Fused floating-point three-term adder. Also, the three fused floating-point units are implemented for both single and double precision and evaluated in terms of the area, power consumption, latency and throughput. To improve the performance of the fused floating-point add-subtract unit, a new alignment scheme, fast rounding, two dual-path algorithms and pipelining are applied. The improved fused floating-point two-term dot product unit applies several optimizations: a new alignment scheme, early normalization and fast rounding, four-input leading zero anticipation (LZA), dual-path algorithm and pipelining. The proposed fused floating-point three-term adder applies a new exponent compare and significand alignment scheme, double reduction, early normalization and fast rounding, three-input LZA and pipelining to improve the performance. / text