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Chapter 7
Series-Parallel Circuits
Objectives
Analyze series-parallel circuitsAnalyze loaded voltage dividersAnalyze ladder networks Analyze a Wheatstone bridge
Basic Idea
Given a circuit; steps to analyze a circuit:Find the total resistance
Determine all parallel resistors and series resistors
Simplify the given circuit Use KCL and Ohm’s law to find all currentsUse Ohm’s law to find all voltages
Find the total resistance
R1 + R2 || R3 + R4 || R5
Find the total resistance
R1 + R6 || (R5 + (R4 || (R2 + R3)))
R1 || (R2 + R3 || (R5 || R4))
Find RT, IT, I2, and I4; Vs=50V
Find RT, I(RL1), I3
Find RT, IT, I2
Find RT, IT and V(AB) VS=10V
Loaded Voltage Dividers
When a load resistor RL is connected from the output to ground, the output voltage is reduced by an amount that depends on the value of RL.
Loading Effect of a Voltmeter
Multimeter
L
LloadR
RRRR
2
2
What happens if RL >> R2?
So, what is the internal resistance of a DMM?
Analysis of a Ladder Network A resistive ladder network
is a special type of series-parallel circuit.
One form of ladder network is commonly used to scale down voltages to certain weighted values for digital-to-analog conversion Called R/2R Ladder
Network To find total resistance of a
ladder network, start at the point farthest from the source and reduce the resistance in steps.
The R/R2 Ladder Network
Only Input 4 is HIGH
Only Input 3 is HIGH
Used for Digital-to-analog converter!
Examining Digital-to-Analog Conversion
For Extra credit: Change the circuit to generate this output:
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