lecture 101 Capacitors (5.1); Inductors (5.2); LC Combinations (5.3) Prof. Phillips March 7, 2003

lecture 102 Energy Storage Elements Capacitors store energy in an electric field. Inductors store energy in a magnetic field. Capacitors and inductors are passive elements: –Can store energy supplied by circuit –Can return stored energy to circuit –Cannot supply more energy to circuit than is stored.

lecture 103 Power Generation and Distribution Energy storage elements model information and power –Capacitors are important components of electronics (logic circuits, filters and power supplies). –Inductors are important for power and communications (motors, radio).

lecture 104 Signal Processing Communication Instrumentation Capacitors and inductors are used to build filters and amplifiers with desired frequency responses: –Instrumentation amplifiers. Capacitors are used in analog-to-digital (A/D) converters to hold a sampled signal until it can be converted into bits.

lecture 105 Solid State Digital Design Integrated circuits (ICs) have layers of conductors (metal, silicon with impurities) with insulators (glass) between. This is a capacitor! This capacitance is one of the limiting factors in processor speeds. This capacitance is used to create RAMs.

lecture 106 Electromagnetics For high frequency signals, inductance and capacitance are more significant effects than resistance.

lecture 107 Capacitance Capacitance occurs when two conductors (plates) are separated by a dielectric (insulator). Charge on the two conductors creates an electric field that stores energy

lecture 108 Capacitance The voltage difference between the two conductors is proportional to the charge: q = C v The proportionality constant C is called capacitance. Units of Farads (F) – Coulomb/Volt

lecture 109 Capacitor i(t) + – v(t) The rest of the circuit

lecture 1010 Capacitor Voltage

lecture 1011 Energy Stored

lecture 1012 Inductance Inductance occurs when current flows through a (real) conductor. The current flowing through the conductor sets up a magnetic field that is proportional to the current. The voltage difference across the conductor is proportional to the rate of change of the magnetic field.

lecture 1013 Inductance The voltage difference across the inductor is proportional to the rate of change of the current. The proportionality constant is called the inductance, denoted L Units of Henrys (H) - V·s/A

lecture 1014 Inductor i(t) + – v(t) The rest of the circuit H

lecture 1015 Inductor Current

lecture 1016 Energy Stored

lecture 1017 Inductor Combinations Series inductors combine like series resistors L ser = L 1 + L 2 + L 3 + · · · Parallel inductors combine like parallel resistors 1/L par = 1/L 1 + 1/L 2 + 1/L 3 + · · ·

lecture 1018 Capacitor Combinations Series capacitors combine like parallel resistors (opposite) 1/C ser = 1/C 1 + 1/C 2 + 1/C 3 + · · · Parallel capacitors combine like series resistors (opposite) C par = C 1 + C 2 + C 3 + · · ·

lecture 1019 Class Examples