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Derivations of the h-Parameters for the BJT Amplifier Using its Characteristics
Adnan Al-Smadi and Qassem Al-Zobi

Transistors are active devices with highly nonlinear characteristics. Therefore, to analyze and design a transistor circuit, a model for the transistor is required. Under small signal conditions, bipolar junction transistors (BJTs) are approximately linear in the forward-active and in the inverse-active regions. The key to transistor small signal analysis is the use of equivalent circuits (or models). Once the ac equivalent circuit has been determined, this model can replace the graphical symbol of the transistor. Then, the basic methods of ac circuit analysis can be used to determine the response of the amplifier. The industrial and educational institutions rely heavily on the hybrid parameters (or h-parameters) equivalent circuit. The manufacturers continue to specify the h-parameter for a particular operating region on the specification sheets. However, specification sheets can not provide parameters for an equivalent circuit at every possible operating point. Hence, the parameters defined at an operating point may or may not reflect the actual operating conditions of the amplifier. This paper addresses a new graphical method for the derivations of the h-parameters.

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