Ionizing radiation detection in harsh environment conditions often requires additional signal processing to match the requirements of the commercial data readout systems. The subject of this paper is the design of the high-temperature (HT) signal conditioning module that ensures the applicability of scintillation detectors that utilize photomultiplier tubes (PMT) with moderate sampling rate instrumentation. The design was developed for the operation in HT environments (up to 120°C). In order to achieve the optimal signal shape, the module combines a charge amplifier and a low-pass filtering circuitry. An embedded power supply section makes it a complete, standalone unit requiring a single 12 V supplying line. A comprehensive analysis of the developed device, named “PreAmp Shape”, was conducted in order to prove the intended functionality over the different working conditions.