Tài liệu Circuits & Electronics P22 pdf

6.002 Fall 2000 Lecture 1 22 6.002 CIRCUITS AND ELECTRONICS Energy and Power 6.002 Fall 2000 Lecture 2 22 Why worry about energy? small batteries Æ good Today:  How long will the battery last? in standby mode in active use  Will the chip overheat and self-destruct? - 6.002 Fall 2000 Lecture 3 22 Look at energy dissipation in MOSFET gates Let us determine standby power active use power Let’s work out a few related examples first. C: wiring capacitance and C GS of following gate V S C R O v + – I v + – 6.002 Fall 2000 Lecture 4 22 Example 1: Power Energy dissipated in time T R V VIP 2 == VITE = + – R I V + – V 6.002 Fall 2000 Lecture 5 22 Example 1: for our gate ONL S RR V P + = 2 0=P O v S V ON R L R I v high S V ON R L R O v I v low 6.002 Fall 2000 Lecture 6 22 Example 2: Consider Find energy dissipated in each cycle. Find average power . P S V + – 1 R C 2 R 1 S 2 S openS closedS 2 1 t closedS open S 2 1 1 T 2 T T 6.002 Fall 2000 Lecture 7 22 T 1 : S 1 closed, S 2 open t C v S V CR t 1 S 1 e R V − t i 1 S R V + – C v + – 1 R C S V i assume v C = 0 at t = 0 6.002 Fall 2000 Lecture 8 22 Total energy provided by source during T 1 dtiVE 1 T 0 S ∫ = dte R V CR t T 0 1 2 S 1 1 − ∫ = 1 1 T 0 CR t 1 1 2 S eCR R V − −=         −= − CR T 2 S 1 1 e1VC 1 2 S1 2 S RindissipatedVC 2 1 E ,ConstoredVC 2 1 = CRTifVC 11 2 S >>≈ I.e., if we wait long enough Independent of R! 6.002 Fall 2000 Lecture 9 22 T 2 : S 2 closed, S 1 open + – C v 2 R C So, initially, 2 S CV 2 1 = energy stored in capacitor Assume T 2 >> R 2 C So, capacitor discharges ~fully in T 2 So, energy dissipated in R 2 during T 2 2 S2 CV 2 1 E = E 1 , E 2 independent of R 2 ! Initially, v C = V S (recall T 1 >> R 1 C ) 6.002 Fall 2000 Lecture 10 22 Putting the two together: Energy dissipated in each cycle 2 S 2 S CV 2 1 CV 2 1 += 21 EEE += C gdischargin & charging indissipatedenergyCVE 2 S = Assumes C charges and discharges fully. frequency T f 1 = T E P = T CV S 2 = fCV S 2 = Average power [...]... t 1 T= f Lecture 22 11 Equivalent Circuit RL VS + – C RON What is P for the following input? vIN T 2 T 2 T 6.002 Fall 2000 t 1 T= f Lecture 22 12 What is P for gate? We can show (see section 12.2 of A & L) 2 P= 2 VS RL 2 + CVS f 2( RL + RON ) (RL + RON )2 when RL >> RON 2 VS 2 P= + CVS f 2 RL er mb me re P STATIC independent of f MOSFET ON half the time 6.002 Fall 2000 be em rem r P DYNAMIC related . show (see section 12.2 of A & L) () () 2 ONL 2 L 2 S ONL 2 S RR R fCV RR2 V P + + + = fCV R2 V P 2 S L 2 S += when R L >> R ON What is for gate?. 1 e1VC 1 2 S1 2 S RindissipatedVC 2 1 E ,ConstoredVC 2 1 = CRTifVC 11 2 S >>≈ I.e., if we wait long enough Independent of R! 6.002 Fall 2000 Lecture