In this video, the small-signal model and the small-signal approximation of the BJT is explained. By watching this video, you will learn the following topics: 0:00 Introduction 0:53 The concept of Transconductance 3:26 What is Small Signal Approximation 9:30 BJT- Small-Signal Model BJT- Small-Signal Model: When BJT is used as an amplifier, the small-signal model of the BJT is helpful in finding the amplifier characteristics. ( Voltage Gain, Input and Output Impedance) BJT- Small Signal Approximation: The small-signal model if the BJT can be used when the input to the BJT is very small. (When Vin us less than Vt (Thermal Voltage)). When the input is very small, then it can be assumed that the BJT is operating in the linear region of the characteristic curve. And hence it is possible to analyze DC and AC signals separately. The transconductance: The transconductance is the measure of how the change in the base-emitter voltage gets translated to the change in the collector current. Transconductance (gm) = ΔIc / ΔVBE. Unit - A/V or Siemens For the small-signal, as ΔVBE is very small it can be expressed as dIc/ dVbe. And transconductance gm = Ic/ VT In this video, after the explanation of the small-signal approximation, the small-signal model of the BJT is explained. This video will be helpful to all the students of science and engineering in understanding the small-signal model of the BJT. #BJT #BJTSmallSignalModel -------------------------------------------------------------------------------------------------- Follow me on Youtube: null Follow me on Facebook: https://www.facebook.com/ALLABOUTELECRONICS/ Follow me on Instagram: https://www.instagram.com/all_about.electronics/ -------------------------------------------------------------------------------------------------- Music Credit: http://www.bensound.com/