Small-signal Amplifier with Three Dissimilar Active Devices in Triple Darlington Topology

Abstract: A new circuit model of a small-signal amplifier is proposed and analyzed on the qualitative scale. Apart from routine biasing components, the proposed amplifier circuit uses two additional biasing resistances and three dissimilar active devices namely MOSFET, JFET and BJT in Triple Darlington configuration. Having a considerably low amount of distortion (0.71%), the proposed circuit successfully amplifies small-signals of 1-5mV range (at 1 KHz frequency) and simultaneously provides high voltage gain (189.846) and high current gain (16.542K) with moderate range bandwidth (369.529KHz). These properties offer a flexible application range to the proposed circuit as high voltage gain or high current gain or high power gain amplifier in permissible audio-frequency range. Variations in voltage gain as a function of frequency and different biasing resistances, temperature dependency of performance parameters, bandwidth and total harmonic distortion of the amplifier are perused to provide a wide spectrum to the qualitative studies. Qualitative performance of the proposed amplifier is also compared with two different circuits which are respectively having BJT-JFET and BJT-MOSFET in Darlington pair configuration. The proposed amplifier may be useful for those applications where high voltage and current gain would be the prime requirement of amplification in audio frequency region

Qualitative analysis of small-signal modified Sziklai pair amplifier

272-276A small-signal modified Sziklai pair (complementary Darlington pair) amplifier is proposed with an additional biasing resistance in the circuit. The proposed amplifier produces significantly high voltage gain with narrow bandwidth. Poor response of conventional Darlington pair amplifiers at higher frequencies is found to be absent in the proposed amplifier circuit. Variations in voltage gain as a function of frequency and different biasing resistances, bandwidth and total harmonic distortion of the amplifier have also been studied. Proposed amplifier may be useful for various analog communication applications