Building logic gates

Power and Energy Power is drawn from a voltage source attached to the VDD pin(s) of a chip. Instantaneous Power: P (t ) = I (t )V (t ) Energy: Average Power: 7: Power – Half the energy from VDD is dissipated in the pMOS transistor as heat, other half stored in capacitor When the gate output falls – Energy in capacitor is dumped to GND – Dissipated as heat in the nMOS transistor

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Pass Transistors DC Response Logic Levels and Noise Margins Transient Response RC Delay Models Delay Estimation .Pass Transistors We have assumed source is grounded What if source 0? VDD – e.g. pass transistor passing VDD VDD Vg = VDD – If Vs VDD-Vt, Vgs Vout = VDD – When Vin = VDD - Vout = 0 VDD – In between, Vout depends on Idsp transistor size and current Vin Vout – By KCL, must settle such that Idsn Idsn = |Idsp| – We could solve equations – But graphical solution gives more insight...

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Nonideal Transistor Behavior – High Field Effects • Mobility Degradation • Velocity Saturation – Channel Length Modulation – Threshold Voltage Effects • Body Effect • Drain-Induced Barrier Lowering • Short Channel Effect – Leakage • Subthreshold Leakage • Gate Leakage • Junction Leakage Process and Environmental Variations .Ideal Transistor I-V Shockley long-channel transistor models

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So far, we have treated transistors as ideal switches An ON transistor passes a finite amount of current – Depends on terminal voltages – Derive current-voltage (I-V) relationships Transistor gate, source, drain all have capacitance – I = C (∆V/∆t) - ∆t = (C/I) ∆V – Capacitance and current determine speed .MOS Capacitor Gate and body form MOS capacitor V Vt + inversion region depletion region .Terminal Voltages Vg Mode of operation depends on Vg, Vd, Vs + + – Vgs = Vg – Vs Vgs Vgd – Vgd = Vg – Vd Vs Vd – Vds = Vd – Vs...

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A Brief History 1958: First integrated circuit – Flip-flop using two transistors – Built by Jack Kilby at Texas Instruments  2010 – Intel Core i7 µprocessor • 2.3 billion transistors – 64 Gb Flash memory • 16 billion transistors 53% compound annual growth rate over 50 years – No other technology has grown so fast so long  Driven by miniaturization of transistors – Smaller is cheaper, faster, lower in power! – Revolutionary effects on society .Annual Sales 1019 transistors manufactured in 2008 – 1 billion for every human on the planet...

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Integrated circuits: many transistors on one chip. Very Large Scale Integration (VLSI): bucketloads! Complementary Metal Oxide Semiconductor – Fast, cheap, low power transistors Today: How to build your own simple CMOS chip – CMOS transistors – Building logic gates from transistors – Transistor layout and fabrication Rest of the course: How to build a good CMOS chip

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