With the evolution of communication technology, low-orbit satellite communications have flourished. However, low-orbit satellites require low cost, low power consumption, small size, and they need to operate normally in the harsh radiation environment of outer space. In the traditional integrated circuit design, the influence of radiation on the integrated circuit is not considered, so designing a chip with radiation tolerance for satellite communication is a big challenge. Analog-to-digital converters (ADCs) play a vital role in electronic systems. They bridge analog and digital signals and play a critical role in communication systems. Among various architectures, the successive approximation registers analog-to-digital converter (SAR ADC) is one of the widely used ones, and the comparator is one of the essential parts. In addition, most of the advanced ADCs are digital circuits, so achieving radiation hardening or radiation tolerance of comparators and digital circuits is a topic worthy of study. This thesis proposes a resistor hardening comparator and uses a triple modular redundancy (TMR) architecture to achieve radiation tolerance with an operating voltage of 1.4 volts. Under the test of pulse laser, the proposed resistor hardening comparator, and the use of TMR, do not observe the errors. Under the pulse laser testing, the traditional comparator has a single event upset (SEU). The statistical error rate is 0.0017, and the pulse laser power is 98.9mW. Therefore, the proposed resistor hardening comparator is more robust than conventional comparators.