Demystifying Switched Capacitor Circuits

Advanced Switched-Capacitor Circuit Techniques

251

standby mode), then it can be shown that the average power dissipation is given by

[6]

PkTDRf

V

V

N

in

dd

=

(

)

4 (7.2)

where DR represents the dynamic range (i.e., accuracy), f

N

is the Nyquist signal

bandwidth (i.e., speed), and V

dd

is the power supply voltage. Thus, in contrast to a

digital CMOS IC whose power dissipation decreases in proportion to the square of

V

dd

, an analog CMOS IC may actually consume more power as the supply voltage is

lowered.

Special CMOS process techniques such as the multiple-layer masking [7] can be

used to reduce the threshold voltage of the MOS transistor. Also, the fl oati ...