1. MAE156A October 12, 2006 UCSD H. Ali Razavi

2.  Electric voltage is similar to height difference: - Electrons start moving under voltage difference - Unless there is a barrier - Balls start moving under height difference - Unless there is a barrier - Work (energy) is needed to move electrons in the reverse direction - Work (energy) is needed to move balls in the reverse direction  Operating an electric circuit if very similar to traveling a closed loop on a 3-D Map: New York San Diego Seattle Miami - As one moves around the map depending on selected road: - One goes through different heights - One experiences different energy requirements and losses - As electrons move around the circuit - Electrons go through different potentials - Electrons go through different energy requirements and losses Voltage

3. New York San Diego Seattle Miami Denver Kirchhoff's Voltage Law

4. Kirchhoff's Current Law  Electric currents are very similar to flows Electric Charge # electrons Electron charge Electric Charge Electric Current

5. Conclusion: To determine the dynamics of circuit, write down Kirchhoff's voltage and current laws Question: How “voltage drop across” and “current passing through a component” are related? * In most cases it is modeled linearly Next: Looking at a few of the following components - Resistor - Capacitor - Inductor - Current source - Voltage source - Transducers - Transistors - Switches - Input impedance - Output impedance Main Points: Impedance of component Current passing “through” component Voltage drop “across” component

6. Resistors are devices that show resistance to passing electric current - All devices and materials show such resistance - Resistance is similar to friction in mechanical systems - It is always present - It generates heat (energy loss) - It determines how much voltage difference (force) is required to pass electrons (speed) - A simple mathematical model for resistance is a “linear model”  A resistor is very similar to a mechanical damper Resistors

7. Capacitor are devices that store electrons - Energy storage - It determines how much voltage difference (force) is store electrons (displacement) - A simple mathematical model for capacitor is a “linear model”  A Capacitor is very similar to a spring in mechanical systems Capacitors

8. Inductors are devices that store energy when there is current (movement of electrons) - Energy storage - It determines how much voltage difference (force) to store energy (velocity) - A simple mathematical model for inductor is a “linear model” Inductors  An inductor is very similar to mass in mechanical systems

9. Example 1: Low Pass Filtering using a Capacitor A low pass filter is a device that eliminates “high frequency content” content of signals Case 1: No Filtering Open Close Time Valve High Frequency Input Time Q High Frequency Output Case 2: Low Pass Filtering Open Close Time Valve High Frequency Input Time Q2Q2 Low Frequency Output Open Close Time Switch High Frequency Input Time i High Frequency Output Open Close Time Switch High Frequency Input Time i2i2 Low Frequency Output

10. After http://www.satcure-focus.com/tutor/page4.htm Pump The pump (supply) always make sure the collector tank is filled with pressurized water 1 2 Collector Base Bipolar Junction Transistors Pump 1 2 Collector Base Switch Flow Amplifier -- --- ++ 2 Emitter (n) Base (P+) + ++ + - Emitter Collector (n) 1 -- +++ -- 2 Emitter (n) Base (P+) - ++ - + Collector (n) 1 Switch Current Amplifier npn

11. Field Effect Transistors Silicon (doped with different impurities at different concentrations at different regions) ------ ---- ++++ +++ +++ Drain: n + Source: n + p Dielectric/Insulator (Silicon Oxide) Gate: Metal ---------- ++++ +++ +++ nMOS FET

12. PM Motor 10A: Start/Stall 2A: Continuous V: 10-12V Design Example 1: Objective: To Turn On and Off a Permanent Magnet DC motor using a Micro Processor with the requirement of passing 10A during On Time with 10-12V on motor terminals. Problem 1: 10A is too high current to be provided by Microprocessor Problem 2: Switching it off and on using microprocessor Problem 3: Interfacing components and programming Pin x Microprocessor Idea 1: Use of MOSFET to switch the Motor On/Off Idea 2: Use of Bipolar Transistor to switch the Motor On/Off Concept Generation Risk Reduction Trouble Shooting Optimization Problems DefinitionConcept Generation