MOSFET的原理特性作用及应用.pptVIP

MOSFET 的原理 特性 作用及應用 MOSFET 的全稱 MOSFET 全稱 : Metal Oxide Semiconductor type Field Effect Transistor 金屬氧化物半導體場效應晶體管 又叫絕緣柵場效應管.是指其柵極 處於不導電(絕緣)狀態.輸入阻抗高. The Structure of MOSFET The Structure of MOSFET(cont.) The Structure of MOSFET(cont.) The Structure of MOSFET(cont.) MOSFET 的工作原理 MOSFET 就是利用柵極電壓的大小,來改變半導 體表面感生電荷的大小,從而控制漏極電流的大小. MOSFET 的分類、符號 、優點、缺點、作用 1.分類 增強型 和 耗盡型 兩種 增強型是指vgs=0時,沒有導電溝道,id=0.黨vgsvt時,才有導電溝道,才有id. 耗盡型是指 vgs=0時, 有導電溝道,id不等於0 增強型 又分 N 型 MOSFET 和 P 型 MOSFET 兩種 2. 符號 N MOSFET P MOSFET 3.優缺點 a. 輸入阻抗高 b. 動作快,工作蘋率高. c. 具正溫度係數.並聯可自動均流 d. 耐壓高 e. 導通電流難做大. 4. 作用 主要是作為開關元件 The Specification of MOSFET The Specification of MOSFET(cont.) The gate driver must supply I1 to C1 and I2 to C2 .Because of the Miller effect , I2 may be grater than I1 even though C1 may be 10 times as larger C2. Assume : Vgs=10V , Vdc,in=12V C1=1800pF , C2=150pF , Tr=50nS , Shoot through (Gate Bounce) Capacitive coupling happens especially at Qgd period The Specification of MOSFET(cont.) The Specification of MOSFET(cont.)---Ton ;Toff Output Characteristic Curve of MOSFET(cont.) Output Characteristic Curve Transfer Characteristic Curve of MOSFET(cont.) Transfer Characteristic Curve Gate Charge Diagram and Crossover Equivalent circuits of the MOSFET turn –on equivalent circuit of period t3 – t4 工作區 of MOSFET VGSVT0, VDSVGS-VT 夾止區, 飽和區, 定電流區, 工作區(信號放大區) 工作區 of MOSFET (cont) VGSVT0, VDSVGS-VT 線性區, 未飽和區, 歐姆區 工作區 of MOSFET (cont) ? Ohmic region: Constant resistance region. If drain-to-source voltage is zero, the drain current also becomes zero regardless of gate–to-source voltage. This region is at the left side of VGS – VGS(th) = VDS boundary line (VGS –VGS(th) VDS 0), and in this region, even if the drain current is very large, the power dissipation could be maintained by minimizing the VDS(on). ? Saturation region: Const