A novel type resonant infrared (IR) detector based on microbridge resonators electrothermally excited and piezoresistively detected using polysilicon resistors of negative temperature coefficient of resistance (TCR) was presented. The temperature rise of microbridges due to absorbed infrared radiation reduces the resistance of the excitation resistors and Wheatstone bridges. As a result, both the static component of the exciting power and the Joule heat of Wheatstone bridges accordingly increase with reducing the resistance. It is equivalent to increasing infrared radiation power. From preliminary experimental results, the feasibility of sensing infrared radiation is demonstrated.