Advanced Analog Circuits

Seth PriceDepartment of Chemical Engineering

New Mexico TechRev. 1/26/15

Diodes (PN Junction)

• Diodes conduct in only one direction• Semiconducting device• Resistance is non-linear• Require a “knee” or “turn-on” voltage– Silicon: 0.6-0.7V– Germanium: 0.3V– LED: 1.7V

Diode Vs. Sine Wave

• http://www.duncansonelectric.com/blog/wp-content/uploads/2009/08/23-half-wave-rectifier-1024x368.gif

IV Curve for Diodes

https://learn.sparkfun.com/tutorials/diodes/real-diode-characteristics

Zener Diode

• Diode that is meant to operate in reverse bias region– Very stable, consistent voltage

• Can be used to replace battery, complex resistor network in some situations

Capacitors

• Store energy in an electric field

• Measured in Farads (F)

• Two physical configurations– Parallel plates– Concentric cylinders

Capacitor Combinations

• Series Combination:•1/Ceq = 1/C1 + 1/C2 + … + 1/Cn

• Parallel Combination:•Ceq = C1 + C2 + … + Cn

Capacitor Voltage

• Vc(t): Voltage across capacitor at any time

• Vs: Source voltage• T: Time constant• t: elapsed time

Vc(t) = Vs(1-e-t/T)

Inductors

• Store energy in a magnetic field

• Measured in Henries (H)

• Typically a coil of wire

• Adjustable inductor: slug

Inductor Combinations

• Series Combinations• Leq = L1 + L2 + … + Ln

• Parallel Combinations•1/Leq = 1/L1 + 1/L2 + … + 1/Ln

Inductor Voltage

• V(t): Voltage across Inductor as a function of time

• L: inductance in Henries• di/dt: change in current

with respect to time

V(t) = -L * di/dt

Time Constants

• Time Constant (T): way to characterize time to charge/discharge a capacitor or inductor

• 1*T: 63% of the maximum charge

• 5*T: fully charged

• For a capacitor: T = R*C

• For an inductor: T = L/R

Solenoids

• Changing current induces magnetic field

• Magnetic field moves plunger

• Used in starter motors, valves, latches, etc.

Solenoid Valve

Transformers• Two adjacent inductors that can

influence each other

• Can add an iron core to transformer to increase magnetic field

• No electron travels between inductors– Isolation Transformer

Transistors

• Semiconducting device

• Used as switches, amplifiers, attenuators, impedance matching, etc.

• Two major categories (NPN, PNP)

• Types: BJT, MOSFET, JFET, etc.

Putting it all together…

• DC Power Supply