The function and working principle of the True-Time Delay (TTD) chip has been studied and the chip has been applied in phased array radar. Based on GaAs Pseudomorphic High Electron Mobility Transistor (PHEMT) technology, three broadband millimeter-wave TTD chips are designed and fabricated. The measured results on wafer show that the 6 bit TTD provides 0.446 ps up to 28.125 ps in the frequency range 32 GHz-40 GHz, the TTD phase error for all 64 bit states is -2°~9°, the Insertion Loss (IL) is less than 19 dB, and the 64 states insertion variation is reduced to ±1 dB, the input and output Voltage Standing Wave Ratios (VSWRs) are better than 1.5 on the whole bandwidth; the 4 bit TTD provides 7.142 ps up to 107.148 ps in the frequency range 32~40 GHz, the TTD phase error for all 16 bit states is better than ±12°, the IL is less than 12 dB, and the 16 states insertion variation is reduced to ±1 dB, the input and output VSWRs are better than 2.0 on the whole bandwidth; the 3 bit TTD provides 28.57 ps up to 200 ps in the frequency range 32~40 GHz, the TTD phase error for all 8 bit states is -10 °~22 °, the IL is less than 14 dB, and the 8 states insertion variation is reduced to ±1 dB, the input and output VSWRs are better than 1.8 on the whole bandwidth. The TTD chips are characterized with ultra wideband, large time delay and compact size, and mainly applied to wideband active phased array applications.