ADVANCED ANALOG CMOS IC DESIGN |
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MOS and Bipolar: Modes of Operation and Models Since the MOS transistor is the basic component of device-level analog circuit design, a strong emphasis will be given on its basic theory: structure and definitions; calculation of surface field and potential, total charge, mobile inversion charge, pinch-off voltage, gate capacitance. An analytical core model requiring only 3 parameters will be derived, which conserves the inherent symmetry of the device and describes its large signal behavior from weak to strong inversion. Channel length modulation, short and narrow channel effects, small signal DC and AC models, temperature effects, noise and matching properties will then be presented. The bipolar transistor will be addressed more superficially, within the framework of CMOS technologies: Ebers-Moll model, large and small signal characteristics, noise, temperature effects, vertical bipolar in CMOS, bipolar operation of MOS transistors, special bipolar structures added in BiCMOS. |
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Passive Components and Parasitic Effects Capacitors, resistors, MOS transistors operated as pseudo-resistors, diodes, parasitic channels, latch-up and gate protection. |
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Layout Techniques for Analog Circuits The fact that signals in analog circuits are represented by physical values and cannot be regenerated along the processing path results in various requirements on the layout. Devices must be implemented with a wide variety of sizes and shapes. Controlled absolute values are only required when a change in signal representation is needed, whereas optimally matched devices are the foundation of sound analog design and will be discussed in details. Parasitic components and effects may distort the signals or introduce unwanted noise sources. Their dependence on layout will be examined with emphasis on the long range coupling from digital to low-level analog subcircuits. |
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CMOS Off-Chip Drivers This lecture deals with circuits that are intended to realize the peripheral of some ASIC chip and therefore are optimized for a particular set of specifications. Different overall amplifier topologies are considered. In particular distinction is made between circuit with a DC feedback around the output stage and those that use only an ac feedback. The voltage follower as an output stage is considered together with some very linear configurations based on the follower. The common source push-pull as a large swing output stage is considered in great details. Gain, offset, linearity, speed and stability are analyzed for various possible implementations. Fully differential and more unconventional configurations are also shown. Finally, some examples of amplifiers realized in mixed technologies used in high voltage applications are given. |
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Analog Functional Blocks The lectures start with an introduction on merits of MOSTs versus bipolar transistors in the different positions of an operational amplifier. Then the design procedures are given for optimal op-amp design by means of the pole-zero position and Bode diagrams. A second-order Miller op-amp is discussed in great detail followed by a design procedure for third-order nested Miller op-amps. All of them are optimized towards high GBW, low noise and minimum power consumption. Finally a considerable number of other configurations are discussed and compared, among which a few very-low-voltage fully-differential operational amplifiers, involving internal common-mode feedback. |
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Elementary Building Blocks Current mirrors, differential pair, current references, analog switch, voltage gain cells, source follower, dynamic comparator, dynamic current mirror, principle of switched capacitors, current generation, voltage-to-current conversion, translinear circuits, strong-inversion squarer-divider. |
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Voltage References "Built-In" voltages available in silicon. Circuits extracting thermodynamic voltage kT/q. Circuit extracting the bandgap voltage. Principle and properties of the bandgap voltage reference and its implementation in CMOS. |
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Technology and other Limitations for Analog Design This module focusses on complementary aspects of analog design. It starts with an overview and comparison of different technology variations and families and includes a detailed comparison of bipolar and MOS transistors. The second part discusses analog design limitations beyond SPICE such as random and non-random parameter variations, device breakdown and degradation and environmental effects at chip level. |
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Switched-Capacitor Circuit Design SC circuit blocks: integrators, biquads and linear filter stages, amplifiers, sample-and-hold stages. SC filter design. SC-based Nyquist-rate and delta-sigma ADCs and DACs. Nonideal effects in SC circuits. Comparison of the SC, SI and GmC circuit techniques. |