Abstract: A temperature and supply independent on-chip relaxation oscillator is introduced. This paper proposed a technique to reduce frequency variation of relaxation oscillator. This technique overcomes the disadvantages of traditional compensation methods, which are restricted by on-chip resistance temperature characteristics. Experimental results show that the oscillator exhibits frequency variation of ±0.11% for supply ranging from 1.62 V to 1.98 V and ±0.24% for temperature ranging from 40℃ to 125℃. Compared to conventional methods, frequency variation of this oscillator is reduced by 2/3. This oscillator is designed in TSMC 180-nm 1P5M CMOS process with a supply voltage of 1.8 V and consumes 50 μW when operating at 25 MHz.