<p>This work investigates the effect of the operating temperatures on crucial performance indices such as junction capacitances and small-signal hybrid (h) parameters of a sol–gel derived ZnO bipolar junction transistor (BJT). The study was carried out in the temperature range of 25–100°C, and its impact on the DC input and output current–voltage (I–V) and capacitance–voltage (C–V) characteristics were observed. The forward current gain was found to increase with temperature for all three modes of operation (common emitter (CE), common base (CB), and common collector (CC), i.e., h_fe, h_fb, and h_fc, respectively). Similarly, the leakage currents in all three modes of operation were also found to increase with temperature. The parameters h_i and h_r were found to decrease with an increase in the temperature. In contrast, the output conductance (h_o) increased with the temperature for all three modes of operation. The junction capacitances of both the junctions (emitter–base and collector–base) were found to increase with increasing temperature due to the reduced width of the space-charge region at the emitter–base and the collector–base junction, respectively.</p> Graphical abstract <p></p>