This paper presents a 4-channel commoncathode VCSEL driver array operating up to 6.25 Gb/s per channel for the applications of HDMI 2.0 active optical cables. The proposed VCSEL driver consists of an input buffer, a modified Cherry-Hooper amplifier as a pre-driver, and a main driver with preemphasis to drive a common-cathode VCSEL diode at high-speed full switching operations. Particularly, the input buffer merges a linear equalizer not only to broaden the bandwidth, but to reduce power consumption simultaneously. Measured results of the proposed 4-channel VCSEL driver array implemented in a 0.13-μm CMOS process demonstrate wide and clean eye-diagrams for up to 6.25-Gb/s operation speed with the bias current 2.0 mA and the modulation currents of 3.1 mAPP. Chip core occupies the area of 0.15 x 0.1 μm2 and dissipate 22.8 mW per channel.