Small-Signal Amplifiers with BJT, FET and MOSFET in Triple Darlington Topology
Sachchida Nand Shukla1, Naresh Kumar Chaudhary2
1Sachchida Nand Shukla, Department of Physics and Electronics, Dr. Ram Manohar Lohia Avadh University, Faizabad, India.
2Naresh Kumar Chaudhary, Department of Physics and Electronics, Dr. Ram Manohar Lohia Avadh University, Faizabad, India.
Manuscript received on September 30, 2014. | Revised Manuscript received on October 12, 2014. | Manuscript published on October 30, 2014. | PP: 102-106  | Volume-4 Issue-1, October 2014. | Retrieval Number:  A3488104114/2013©BEIESP

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Abstract: Circuit models of two discretely developed small-signal amplifiers are proposed and qualitatively analyzed perhaps for the first time. Design of first amplifier uses Triple Darlington topology based hybrid unit of BJT-JFET-MOSFET in RC coupled voltage divided biasing network with two additional biasing resistances. However the second amplifier uses JFET-BJT-MOSFET hybrid unit in the similar circuit design. Both the amplifiers successfully amplify small-signals swinging in 1-10mV range at 1KHz frequency. These circuits simultaneously produce high voltage gain (≈ 291 and 345 respectively) and current gain (≈ 719 and 27K respectively) in narrow bandwidth region (≈ 8KHz and 13KHz respectively). Variations of maximum voltage gain with different biasing resistances and DC supply voltage, temperature sensitivity of performance parameters, THDs, small-signal AC equivalent circuit analysis and noise performance of the circuits are elaborately studied and discussed. The proposed amplifiers may be useful for those applications where high voltage and current gain would be the prime requirement of amplification in narrow band frequency region. Moreover, the proposed circuits may also useful for radio and TV receiver stages and low-frequency power sources.
Keywords: Small-signal amplifiers, Darlington amplifiers, Compound Darlington configurations, Triple Darlington topology.