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The operational amplifier, cont.

The operational amplifier, cont. Has a multitude of circuit applications Linear applications Inverter, summer, integrator, etc. Non-linear applications Comparator. Classwork #2. Find v o. Inverting summing amplifier. Op amp non-linear applications.

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The operational amplifier, cont.

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  1. The operational amplifier, cont. • Has a multitude of circuit applications • Linear applications • Inverter, summer, integrator, etc. • Non-linear applications • Comparator

  2. Classwork #2 Find vo

  3. Inverting summing amplifier

  4. Op amp non-linear applications The output voltage is a function of the input voltage difference Op amp can be forced to work in the linear region with feedback Without feedback, the operation is quite different

  5. The comparator • A comparator is a circuit that monitors two input voltages • One is called the reference voltage, and the other the input voltage • The output voltage depends upon the relation between the reference voltage and the input voltage, i.e., whether Vin is larger or smaller than Vref • Op amps operated without feedback can act as comparators

  6. Comparator Reference voltage to positive input Reference voltage to negative input

  7. Comparator circuits Physical outputs Physical signals

  8. Generic comparator circuit Physical and electrical outputs Physical and electrical input signals

  9. Comparator circuits What are RA and RB? Circuit components that convert physical signals to electrical signals by having electrical properties that change with external physical changes. Examples: Thermistors - temperature sensitive resistors Photoconductors - light sensitive resistors Strain gauges - strain sensitive resistors Microphones - sound sensitive components

  10. Comparator circuits Output component examples LEDs driven by op amp output Power transistor stages to drive LEDs, buzzers, relays Other amplifier stages Voltage to frequency converters Analog to digital converters Multimeters Motors Timers, clocks, recorders

  11. Additional circuit components Diode Variable resistor = RV = R1 + R2

  12. Additional circuit components Bipolar junction transistor Transistor Field effect transistor FET ID = IS IC ≈ IE Large current (VG > 0) Large current (IB > 0) ID IC Zero (VG = 0) Zero (IB = 0)

  13. Additional circuit components Relay Sensing resistor Electromechanical device - a small current is used to control a large current R = R(Temperature) R = R(Pressure) R = R(Light)

  14. Example comparator circuit Light activated switch LED is on when input is below Vref Resistance of photoconductor decreases when illuminated

  15. Classwork Building upon ideas from previous circuit, design a Dark Activated Switch

  16. Classwork Build and test this circuit - use a voltmeter to measure voltages in circuit

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