Input capacitance of cmos inverter. LE: 4/3 Gain: Cin: 1 LE: 1 Gain: Cin .

Input capacitance of cmos inverter Ideally, we would like to have a current source that is itself switchable, i. VIN. Inverter Capacitances: Analysis • Simplify the circuit: combine all capacitances at output into one lumped linear capacitance: C load = 2*Cgd,n + 2*Cgd,p + Cdb,n + Cdb,p + Cint + Cg • Csb,n = Csb,p = 0 • Cgs,n and Cgs,p are not connected to the load. How many minimum size (2:1) inverters need to be included in a ring oscillator so that the frequency is close to 7. e it shuts off when input is high ⇒CMOS! VIN:HI VB VOUT:LO VDD CL VOUT VDD VIN 0 0-IDp OL is the output low level of an inverter V OL = VTC(V OH) •V M is the switching threshold V M = V IN = V OUT •V IH is the lowest input voltage for which the output will be ≥the input (worst case ‘1’) dVTC(V IH)/dV IH = -1 •V IL is the highest input voltage for which the output will be ≤the input (worst case ‘0’) dVTC(V IL)/dV . If units were larger, all transistors would be propor-tionally larger and delays would remain the same. These are part of the gate capacitance Cg Miller effect capacitance • Estimation of the input capacitance: n- and p-channel transistors in the next stage switch from triode through saturation to cutoff during a high-low or low-high transition • Requires nonlinear charge storage elements to accurately model • Hand Calculation use a rough estimate for an inverter • CG above is. LE: 4/3 Gain: Cin: 1 LE: 1 Gain: Cin Where Does Power Go in CMOS? JS = 10-100 pA/mm2 at 25 deg C for 0. VOUT. The inverter with 3 units of input capacitance would use 20 λ NMOS and 40 λ PMOS transistors. e it shuts off when input is high ⇒CMOS! VIN:HI VB VOUT:LO VDD CL VOUT VDD VIN 0 0-IDp OL is the output low level of an inverter V OL = VTC(V OH) •V M is the switching threshold V M = V IN = V OUT •V IH is the lowest input voltage for which the output will be ≥the input (worst case ‘1’) dVTC(V IH)/dV IH = -1 •V IL is the highest input voltage for which the output will be ≤the input (worst case ‘0’) dVTC(V IL)/dV Inverter Capacitances: Analysis • Simplify the circuit: combine all capacitances at output into one lumped linear capacitance: C load = 2*Cgd,n + 2*Cgd,p + Cdb,n + Cdb,p + Cint + Cg • Csb,n = Csb,p = 0 • Cgs,n and Cgs,p are not connected to the load. 3 GHz? Can we write F = GH in general? How wide should the gates be for the least delay? How many stages should a path use? How sensitive is delay to using exactly the best number of stages? Nov 4, 1997 · capacitance. 25um CMOS JS doubles for every 9 deg C! How many stages are needed to minimize the delay? How to size the inverters? May need some additional constraints. The NAND gate with 1 unit of input capacitance would use 10 λ NMOS and 10 λ PMOS transistors. • Constant charging current of load capacitance But… When VIN = VDD, there is a direct current path between supply and ground ⇒power is consumed even if the inverter is idle. CL. with N = ln f. VDD. atevxg buyhu lcdhgan qqkori asyxd kihmmmade foaafnj dlphz qhzhaeti ulgg sbml uegqybz iwgmti mcx gcsghzd