Design of a DC-33 GHz cascode distributed amplifier (DA) using dual-gate device in 0.5-μm GaAs enhancement/depletion-mode (E/D-mode) high electron mobility transistor (HEMT) process is presented in this paper. A compact dual-gate HEMT is adopted in the gain cell of the DA. By using the dual-gate HEMT, the gain-bandwidth product of the DA can be further improved. The proposed DA achieves a small-signal gain of 10.6 dB, an output power 1-dB compress point (OP1dB) of 8.9 dBm, and a 3-dB bandwidth from dc to 33 GHz. The DA is also successfully evaluated using pseudorandom bit stream (PRBS) signal with a data rate up to 12-Gbps. The proposed dual-gate DA is suitable for the high-speed data rate transmission due to its superior performance.