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MOSFET: Subthreshold Operation Professor Paul Hasler.

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Presentation on theme: "MOSFET: Subthreshold Operation Professor Paul Hasler."— Presentation transcript:

1 MOSFET: Subthreshold Operation Professor Paul Hasler

2 MOSFET Channel Picture

3 MOS Capacitor Picture

4 MOSFET Channel Picture

5

6 Calculation of Drain Current

7 No recombination 0 2 2  dx nd DnDn n dn qDJ  l nn drainsource n  0 l  varies as  V G  n = Ax + B RG dx nd D dt dn n    2 2 0 00  (qD n / l) ( e -(  - Vs)/UT - e -(  - Vd)/UT )   eeII uVVuVV TdgTSg   / / 0 

8 MOSFET Current-Voltage Curves   1 /)( 0 //)( 0 / // 0 TSG TdSTSG TD TSTG uVKV uVuV uV uVu DS eI eeI eeeII          eeII uVVuVV TdgTSg   // 0     1 / / 0 TSd TSg uVV uVV eeI    

9 Channel Current Dependence on Gate Voltage In linear scale, we have a quadratic dependence In log-scale, we have an exponential dependence

10 Channel Current Dependence on Gate Voltage In linear scale, we have a quadratic dependence In log-scale, we have an exponential dependence

11 Subthreshold MOSFETs In linear scale, we have a quadratic dependence In log-scale, we have an exponential dependence G S D nFET G S D B pFET

12 Determination of Threshold Voltage 0.40.50.60.70.80.91 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 Gate voltage (V) Drain current / subthreshold fit V T = 0.86

13 Drain Current --- Source Voltage


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