This paper presents a 4-40 Gb/s PAM-4 transmitter using a novel hybrid driver. Different from conventional current-mode (CM) drivers with poor linearity and source-series terminated (SST) drivers with limited differential output swing, the proposed hybrid driver delivers a differential output swing exceeding the supply voltage with high linearity using a combination structure of the CM and SST driver. In addition, a 4-40 Gb/s quarter-rate transmitter with one-tap feedforward equalization is designed in 65nm CMOS technology using the hybrid driver, yielding a 1.8V differential peak-to-peak output swing at 1.2 V supply voltage with a 96.4% ratio of level mismatch.