2. RESISTIVE CIRCUITS CIRCUITS by Ulaby & Maharbiz Piezoresistive sensor All rights reserved. Do not reproduce or distribute. ©2013 Technology and Science

2. RESISTIVE CIRCUITS

CIRCUITS by Ulaby & Maharbiz

Piezoresistive sensor

All rights reserved. Do not reproduce or distribute. ©2013 Technology and Science Press

All rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

Ohm’s Law

Voltage across resistor is proportional to current

iR

Resistance: ability to resist flow of electric current

iR

r = resistivity


ConductivityAll rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

Resistor Codes


Example 2-1: dc Motor

= 98% of P

What fraction of power supplied by the battery is dissipated in the motor?

Solution:



Tech Brief 2: Superconductivity

Critical temperature TC is the temperature at which a material becomes superconducting (zero resistance & no power dissipation)


Kirchhoff’s Current Law

Sum of currents entering a node is zeroAlso holds for closed boundary


Example


Kirchhoff’s Voltage Law (KVL)

Sum of voltages around a closed path is zero

Sum of voltage drops = sum of voltage rises


Example : KCL/KVL

Determine all currents & voltages

Solution:

Three equations w/three unknowns:

Loop 1

Loop 2



Equivalent Circuits

If the current and voltage characteristics at nodes are identical, the circuits are considered “equivalent”

Identifying equivalent circuits simplifies analysis


Resistors in Series

Equivalent resistance (series) is sum of resistances

Voltage divided over resistors (voltage divider)


Adding Sources In Series

Unrealizable Circuit

Combining voltage sources


Resistors in ParallelAll rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

Source Transformation

Hence,

For the two circuits to be equivalent :


Example 2-10: Source Transformation


Circuit with no two resistors sharing the same current or same voltage

R1,R2,R3=Delta

R3,R4,R5=Delta

R2,R3,R5=Y

R1,R3,R4=Y


Between nodes 1 and 2:

( Assuming no connection at node 3)

Hence,


Simultaneous solution leads to:


Example 2-12: Y-Δ CircuitAll rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press


Wheatstone Bridge

Measurement instrument based on differential measurement

Balanced Condition:

Determine unknown resistance based on “balanced” condition

For balanced condition


Wheatstone Sensor

Determine Vout


Tech Brief 3: Resistors As Sensors Piezoresistive Sensors


Tech Brief 3: Resistors As Sensors


Tech Brief 3: Resistors As Sensors

Thermistor Sensors


Example 2-16: Piezoresistor Cantilever

(400 times greater than w/o cantilever)


Linear i-v relationships


The Diode

Current can flow only from + to – through a diode.



Multisim

SPICE simulator software Powerful tool for analyzing circuits See tutorial and examples on CD that

accompanies the text


Multisim: Creating a CircuitAll rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

Multisim: DC Operating Point Solution


Multisim Solution WindowAll rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

SummaryAll rights reserved. Do not reproduce or distribute. © 2013 National Technology and Science Press

Documents

2. RESISTIVE CIRCUITS CIRCUITS by Ulaby & Maharbiz Piezoresistive sensor All rights reserved. Do not reproduce or distribute. ©2013 Technology and Science