tailieunhanh - Analog Electronics with Labview P2

Characterization of MOS Transistors for Circuit Simulation In this unit, the basic (Level 1 SPICE) dc MOSFET characteristic equations are introduced. The amplifier exercises and projects use the results for design and analysis. Circuit solutions are compared with measured results from the circuit to make an assessment of the degree to which the transistor models for the MOSFET represent actual device behavior. The parameters for this unit are presented in Table . Note that in the case of KP, we can only measure K and would be able to extract KP only if gate width W and length L were known | Unit 3. Characterization of MOS Transistors for Circuit Simulation In this unit the basic Level 1 SPICE dc MOSFET characteristic equations are introduced. The amplifier exercises and projects use the results for design and analysis. Circuit solutions are compared with measured results from the circuit to make an assessment of the degree to which the transistor models for the MOSFET represent actual device behavior. The parameters for this unit are presented in Table . Note that in the case of KP we can only measure K and would be able to extract KP only if gate width W and length L were known. TABLE SPICE Name Math symbol Description VTO Vtno Vtpo Zero-bias threshold voltage. KP KP W 2 L Transconductance parameter. Gamma Yn Yp Body-effect parameter. Phi 2 l Surface inversion potential. Lambda Xn Xp Channel length modulation. Physical Description of the MOSFET A diagrammatic NMOS is shown in Fiq. . The device consists of a three-layer structure of metal-oxide-semiconductor MOS . A two-terminal MOS structure connections to metal and semiconductor is essentially a parallel-plate capacitor. In the same manner as for a normal capacitor when a positive gate voltage Vg is applied with respect to the p-type body for NMOS . with respect to the metal contact on the underside of the p-type semiconductor body or substrate negative charges are induced under the oxide layer in the semiconductor. When Vg with respect to the semiconductor body exceeds the threshold voltage Vtno a channel of free-carrier electrons forms under the oxide that is the onset of the channel occurs when Vg Vtno. The substrate is n type for the PMOS and the channel is made up of free-carrier holes. Figure . MOS transistor consisting of a metal - oxide -semiconductor layered structure plus a metal body contact on the bottom . A positive gate voltage VG Vtno induces a conducting channel under the oxide which connects the two n regions source and drain. All voltages are with respect to VB