This Letter presents a 2 GHz 130 nm CMOS absorptive on–off keying (OOK) modulator. The loop matching technique is proposed to realise wideband matching such that fast modulation envelope transient can be achieved. The parallel LC network is adopted to reduce the impedance variation between the ON and OFF states of the modulator. The CMOS OOK modulator is capable of delivering the modulation data rate of 734 Mbps, leading to the data‐to‐carrier‐ratio of 36.7%.