This paper presents a Mach-Zehnder-based transmitter in 0.18 µm CMOS. An asymmetric driver is proposed to achieve a large output swing on the optical modulator. The logical effort method was applied on each driver block in order to optimize the propagation delay. The driver characteristics are analyzed based on slew-rate limitation. The speed-power-area trade-off is highlighted and enables to adjust the driver design according to specified constraints. Driver performance obtained with early-design-stage equations is compared to post-layout simulations. Good agreement is demonstrated which validates the proposed sizing methodology.