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Operational Amplifiers Digital Simulation. Nate Moehring. Operational Amplifiers. Used in amplifiers, attenuators, and filters Ideal Properties of an Op Amp: Infinite open-loop gain, A ol = infinity Infinite input impedance, R in = infinity Zero output impedance, R out = 0

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Operational amplifiers digital simulation

Operational AmplifiersDigital Simulation

Nate Moehring


Operational amplifiers
Operational Amplifiers

  • Used in amplifiers, attenuators, and filters

  • Ideal Properties of an Op Amp:

    • Infinite open-loop gain, Aol = infinity

    • Infinite input impedance, Rin = infinity

    • Zero output impedance, Rout = 0

    • Zero noise contribution

    • Zero DC output offset

    • Infinite bandwidth, infinite frequency response

    • Both differential inputs stick together


Why use op amps
Why use op amps?

  • Extremely high gain (10,000x)

  • Infinite input resistance good for adding multiple sources (0 current = 0 voltage drop)

  • Develop high pole filters


Example
Example

  • Passive Band Pass


Example1
Example

  • Active Band Pass


Example2
Example

  • Active Band Pass w/ amplifier


Op amp configurations
Op Amp configurations

Comparator

  • Rails +/- to higher input

  • (Takes difference

  • Multiplies by 10,000)


Op amp configurations1
Op Amp configurations

Inverting Gain

  • Vo = -Vi(Rf/Ri)

  • (Feedback loop creates

    180oout of phase signal

    that eliminates large Aol)


Op amp configurations2
Op Amp configurations

Non - Inverting Gain

  • Vo = Vi(1 + Rf/Ri)

  • (Feedback line

    must always go to negative

    input. Otherwise, we

    would be summing infinitely.)


Op amp configurations3
Op Amp configurations

Buffer – Isolation Amplifier

  • Vo = Vi(1 + 0/) = 1

  • Also called “follow me”

    amplifier.


Op amp configurations4
Op Amp configurations

Filter

  • fc = 1/(2RC)

  • “Active”, although this

    filter is no better than a

    passive filter.


Op amp configurations5
Op Amp configurations

Differential Amplifier

  • Vo = R2/R1(V2-V1)

  • “Subtractor”


Op amp configurations6
Op Amp configurations

Summing Amplifier

  • Vo = V1(R3/R1) + V2(R3/R2)

  • “Adder”


Parametric results w transient
Parametric resultsw/ transient


Parametric results w ac sweep
Parametric resultsw/ AC Sweep


Transistors
Transistors

Bipolar Junction Transistors BJT (npn)

  • Uses a small amount of current to allow a large amount of current to pass through it. (Amplifier) (Flood gate)

  • Also used as “on/off” switch. (Transistor Transistor Logic (TTL))

  • Bipolar.olb

Collector

Base

Emitter


Operational amplifiers digital simulation

NOT Gate

These TTL representations are greatly simplified for logical interpretation and are not meant for actual implementation as seen here.




Digital simulation
Digital Simulation

  • Use Bias Point calculations manually changing VDCs

  • Use Bussed STIM sources to perform transient analysis.

  • Get digital components from 74ac (pro) or Eval library (student)


Using stim sources
Using STIM sources

  • Use STIM4 from source library

  • Draw bus wire

  • Place “Net Alias” ON bus, ie. A[0:3]

  • Use “Bus Entry” tool to extract lines

  • Name lines using Place “Net Alias”

  • Double click STIM4 to create pattern

  • Probe input and outputs

  • Run transient simulation


Voter problem
Voter Problem

  • Build using 74xx logic gates

  • Input manually using VDC sources and view outputs using Bias Voltages

  • Input using STIM4 providing all possible input combinations.