This article presents the design and implementation of a broadband terahertz (THz) detector chip based on 180 nm CMOS technology, which supports both direct detection and heterodyne detection modes. The detector consists of a loop antenna, a NMOS transistor differential detection circuit, and an impedance matching network, with an area of 200 × 200 μm2. Based on the bidirectional radiation characteristics of the loop antenna, a layout scheme is proposed to separate the radio frequency (RF) and local oscillator (LO) on both sides of the detector, this scheme does not require the use of a beam splitter to couple the signal, thus avoiding signal attenuation. The LO signal is generated by an external independent terahertz wave source, which has advantages in frequency stability and output power compared to on-chip integrated LO. In order to suppress the surface wave loss of the silicon substrate, a high resistance silicon lens with a diameter of d=12 mm and a thickness of t=8 mm is integrated on the back of the chip. The test results show that the operating frequency range of the detector covers 75-325 GHz, and the heterodyne detection of noise equivalent power (NEP) is superior to direct detection of NEP by more than three orders of magnitude. The detector exhibited optimal performance at the frequency of 220 GHz, with a heterodyne detection NEP of 6.26 fW/Hz and a direct detection NEP of 18.42 pW/Hz1/2.