The goal of this thesis is to design the readout electronics for the photodetector which is going to be used on a satellite. The circuitry consists of a transimpedance amplifier (TIA) and additional passive components, while the photodetector is a classic PIN diode. The final application is the radiation detection on the satellite deployed by the Faculty of electrical engineering and computing, University of Zagreb (FERSAT). In this thesis, which presents the first draft, a PIN photodiode is used to detect ultraviolet light, whereas the final version of the circuit will utilize a PureB photodetector, used for the first time to detect UV light and electron density in outer space. Since PureB photodiodes are going to be mounted on the satellite, measurements of aforementioned detectors are carried out considering their dimensions and characteristics. The circuitry design and detailed computer analysis are made on LTspice software, where fundamental simulations are done and the effects of individual components on the output voltage and amplitude-frequency characteristics are observed. Optimal design, one giving the desired outputs, is implemented on a printed circuit board with Altium Designer software. Then, after the designing stage, the PCBs were measured and the data was compared to the simulation results.