Dear friends:
Firstly,I must be sure whether BJT or MOSFET can transform using laplace transform.Secondly,If it can transform,I want to know how to finish .
Dear FvM:
If transistors can not imagine to model it with laplace,please you list other ways.especially,how to build a mathematical model
of transistors in the actual circuit.
You didn't tell which aspects of transistor behaviour you want to model. In circuit simulation, transistors are usually modelled by non-linear equations, e.g. Gummel-Poon model for BJT.
You didn't tell which aspects of transistor behaviour you want to model. In circuit simulation, transistors are usually modelled by non-linear equations, e.g. Gummel-Poon model for BJT.
Dear FvM:
I can use non-linear differential equation to define the current of BJT model in circuit. But why can operational amplifier circuit show laplace model.example,Active low-pass filtering amplifier ciruit.
according to the structure of operational amplifier ,I realize operational amplifier is made up of lots of BJT.could you tell me why BJT cannot be shown in Laplace.then operational amplifier can be shown.
Analysis of active filters and many other OP circuits is presuming small-signal operation, linearizing the non-linear transfer characteristic around the bias point. The same can be done for analysis of transistor circuits. It uses small signal transistor models, see https://en.wikipedia.org/wiki/Transistor_model#Small-signal_linear_models
Also albbg is talking about small signal transistor models in post #3.
Dear FvM:
If I can understand when Transistor works in the area of linear,transistor can be transformed using laplace.however,when transistor runs in the area of non-linear,it cannot be modeled in any mathematics method。
Dear albbg:
If I can understand when Transistor works in the area of linear,transistor can be transformed using laplace.however,when transistor runs in the area of non-linear,it cannot be modeled in any mathematics method。
Nonlinear systems can be well described by nonlinear differential equations, also transistors. Transient analysis of circuit simulators is using it extensively.