Analysis and calculation of circuit parameters

Circuit parameters analysis and calculation techniques are divided into linear and nonlinear ones. Before choosing one of two methods it is

necessary to define if a transistor is a linear component in this case or not. The comparative length of a transistor characteristic can be considered as a sufficient criterion. The transistor’s operating point is moving within that length of characteristic during amplification of a desired signal. In the low amplitudes mode of the input signal the operating point moves within the slight region of a characteristic. It is possible to consider that the region is rectilinear and then, a transistor can be counted as a linear component.

In the high amplitudes mode of the input signal the transistor’s operating point moves almost along the entire transistor characteristic which is nonlinear.

In the low amplitudes mode the transistor is defined by low signal parameters, and the linear methods such as four-terminal, equivalent circuits, matrix can be used for calculations.

The output stages of electronics operate in the high amplitudes mode and the transistor is described by a non-linear model. It has to be analyzed and calculated by non-linear methods. One of them is the grapho-analytical method.