Lect.6.Intrinsic.Cap

E c h a n n e l c h a r g e this means cgd0 in the

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: n e l m o d e l fo r a c tiv e ( s a tu r a tio n ) o p e r a tio n , th e d r a in v o lta g e d o e s n o t a ffe c t th e c h a n n e l c h a r g e – This means Cgd=0 in the saturation region! • Neglecting second order effects and extrinsic caps, of course R. Dutton, B. Murmann EE114/214A 16 T r a n s is t o r O f f G S D W L C GC xd C CB • T h e r e is n o c o n d u c tiv e c h a n n e l – G a te s e e s a c a p a c ito r to s u b s tr a te , e q u iv a le n t to th e s e r ie s c o m b in a tio n o f th e g a te o x id e c a p a c ito r a n d th e d e p le tio n c a p a c ita n c e • If th e g a te v o lta g e is ta k e n n e g a tiv e , th e d e p le tio n r e g io n s h r in k s , a n d th e g a te - s u b s tr a te c a p a c ita n c e g r o w s – With large negative bias, the capacitance approaches CGC R. Dutton, B. Murmann EE114/214A 17 In t r in s ic M O S C a p a c it o r S u m m a r y Subthreshold Triode Saturation Cgs 0 ½ WLCox Cgd 0 ½ WLCox 0 Cgb '1 1$ % " + %C WLCox " & CB # 0 0 Cgd Cgb Cgs CCB = R. Dutton, B. Murmann ! Si WL xd EE114/214A 2/ 3 WLCox !1 xd is the width of the depletion region at the silicon surface 18 C o m m o n S o u r c e A m p lif ie r R e v is it e d • A s s u m in g th a t th e tr a n s is to r o p e r a te s in th e s a tu r a tio n r e g io n , w e c a n c o n s tr u c t th e fo llo w in g s m a ll- s ig n a l m o d e l – Important to note that we are still neglecting e...
View Full Document

Ask a homework question - tutors are online