MOSFET Biasing

ELEC 121

January 2004 ELEC 121 2

D-MOSFET Self Bias

January 2004 ELEC 121 3

Determining the Q-point for D-MOSFET Self Bias

January 2004 ELEC 121 4

N Channel D-MOSFET Voltage Divider Bias

January 2004 ELEC 121 5

Q Point of D-MOSFET Voltage Divider Bias

January 2004 ELEC 121 6

Effect on Change in Q Point with Variation of RS

With an N ChannelD-MOSFET, VGS may be positive

January 2004 ELEC 121 7

D-MOSFET Fixed Bias

January 2004 ELEC 121 8

E-MOSFET Feedback Bias

January 2004 ELEC 121 9

DC Equivalent For the E-MOSFET Feedback Bias

IG = 0

VGS = VDS

January 2004 ELEC 121 10

Transfer Curve for the E-MOSFET Feedback Bias

January 2004 ELEC 121 11

Determining the Q-point for E-MOSFET Feedback Bias

January 2004 ELEC 121 12

Q-point for the E-MOSFET Fixed Bias

January 2004 ELEC 121 13

EMOS Feedback Bias Example

VGSTH = 4VVGSon = 7.5VIDon = 5mAVDD = 22V

Don

2GSon GSTH

2D GS GSTH

I k =

(V - V )

I = k(V - V )

January 2004 ELEC 121 14

EMOS Feedback Example

January 2004 ELEC 121 15

Voltage Divider Bias for an N E-MOSFET

2G DD

1 2

Don

2GSon GSTH

2D GS GSTH

R V = V

R +R

I k =

(V - V )

I = k(V - V )

January 2004 ELEC 121 16

Voltage Divider Bias for an N E-MOSFET

2G DD

1 2

G GS D S

Don

2GSon GSTH

2D GS GSTH

R V = V

R +R

-V + V + I R = 0

I k =

(V - V )

I = k(V

KVL Input

- V )

January 2004 ELEC 121 17

Voltage Divider Bias for an N E-MOSFET

January 2004 ELEC 121 18

Q-point for E-MOSFET Voltage Divider Bias