Laptop Adapter Design--What Is The Difference Between The MOSFET And The Transistor In The On State?

- Jun 08, 2018 -

  MOSFET is a very wide range of field-effect transistors that are used in analog circuits and digital circuits. The transistor is also a bipolar transistor that can control the flow of current and amplify smaller signals into higher-amplitude electrical signals. Both the MOSFET and the transistor have an on state, so what is the difference between the two when it is on?

 MOSFET and transistor, when on state, the MOSFET usually uses the RDS, the transistor usually uses the saturated VCE. So is there a case where the transistor is saturated with rce, and the MOSFET uses saturated VDS?

 Transistor on state when working in the saturated zone, the conduction flow ice mainly by the IB and VCE decision, because the transistor's base-driven current IB can not be kept constant, so the ice can not be simply determined by the VCE, that is, can not use saturated rce to express (because Rce will change). Due to the saturation of VCE smaller, so the transistor generally used saturated VCE expression.

 The MoS tube works in the linear area (equivalent to the saturation region of the transistor) in the on State, similar to the transistor, the current IDs are determined by VGS and VDS, but the drive voltage VGS of the MoS tube can generally remain unchanged, so IDs can only be affected by VDS, that is, VGS fixed  

  The conduction impedance RDS basically remains unchanged, so the MoS tube uses the RDS method. The current can flow through the MOSFET's D and S, which is the outstanding advantage of MOSFET, so that there is no concept of DCM in synchronous rectifier, energy can be passed from input to output, or output can be returned to input. can achieve bidirectional energy flow.

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