Development of Low Frequency Small Signal Amplifier using BJT-JFET in Sziklai Pair Topology

A new PSpice Model of BJT and JFET is proposed and its hybrid combination is used in Sziklai pair topology to design small signal amplifier. The proposed amplifier with maximum voltage gain 30.41, maximum current gain 43.05 and THD 2.44% is capable of amplifying low magnitude signals in a frequency range distributed from 3.035Hz to 93.808Hz. This feature explores the possibility to use proposed amplifier circuit in EEG, seismographs and underwater communication circuits. Three different circuit/device combinations are also exposed during the exploration of proposed amplifier and therefore mentioned with primary details. Qualitative behaviour, e.g. temperature dependency, noise behaviour, effect of the variation of biasing resistances and capacitors, small signal AC analysis etc., of the proposed circuit, is also studied to observe its performance under different environment.