Abstarct: For many decades, detecting of high ionizing radiation like X and Gama-ray attracted many attentions to researches in this field. Since, the effects of these radiation on the human body’s tissue can cause devastation and genetic mutation so that it should be minimized as low as possible. The detectors can be used to measure the amount of radiation of the environment especially in the medical application such as fluoroscopy, CT-Scan and etc. One of the first detectors that can be considered to analyze the amount of radioactivity in the environment is Geiger counter. Geiger counter cannot be accessed due to the reasons like being rare, cost, and high-voltage operation. In this thesis, firstly, the detectors baxsed on PIN photodiode are investigated and then three samples of X-ray detector structures baxsed on photodiode are simulated and implemented. The second and third pulse mode detectors have preamplifier structures with feedback impedance, while the first detector has a different structure in the preamplifier. Moreover, the three detectors also differ in the number of pulse shape stages. By comparing the electrical characteristics of the pulse mode detectors' responses, three parameters are investigated like conversion gain, pulse duration, and power dissipation. Among the proposed structures, the second architecture has a conversion gain of 66.75-dB which is the best performance among the other detectors. Moreover, the noise spectral density of the first detector is measured 7.64-nV2 which is the minimum amount. As a matter of fact, the second and third detectors have a pulse duration of 12 and 8.2 μs, respectively. Consequently, it can be inferred that they have a better performance in high count rate. Also, the first detector with a minimum power consumption of 36.6-mW has a better performance among other detectors. It should be noted that the first detector has a simple structure which can lead to decrease the production cost. According to the experimental results, the second and third detectors detect toward the minimum energy (59.54-keV) and the pulse amplitude of the detectors is recognizable than the noise. It should be noted that the first detector does not detect the minimum energy and it cannot be a suitable candidate for this range of the energy. The experimental results of the fourth detector are shown that the amount of the equivalent dose has a relationship with the measured voltage of the circuit in the range of 30 to 800 micro sievert per hour. The SMART technique as one of the multiple-attribute decision-making methods has been used in this research to enable initial decision-making for ranking the photodiodes which are used in this thesis. Using this method, S1223-01, BPV10, BPW34, S186P, PH320, PD438C and BPV23NF were ranked first to seventh, respectively. Also, the mentioned detectors have the ability to be used as a low-cost ionization detector.