Chapter 4
Operational Amplifiers

m4.1 Ideal Op-Amp Model

  1. Determine a general expression for vout in terms of the resistor values and is for the circuit of Figure m4.1.
  2. Find vout for these specific component values: R1 = 3.3 kΩ, R2 = 4.7 kΩ, R3 = 1.0 kΩ, and iS = 1.84 mA.
  3. Determine the range of R2 for which -11 ≤ vout ≤ +11 volts.

PIC


Figure m4.1: Circuit for Problem m4.1

NI Multisim Measurements

  1. Enter the circuit of Figure m4.1 into NI Multisim. Use the virtual three-terminal op amp model.
  2. Measure vout for the given set of component values.
  3. Plot vout as a function of R2 with a Simulate → Analyses → Parameter Sweep analysis of the “DC Operating Point” type. Increase the number of points as needed to ensure an adequate number of measurements to characterized the op amp output voltage in the region of the specified voltage limits.
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NI myDAQ Measurements

  1. Build the circuit of Figure m4.1 with the given component values. Implement the current source Isrc1 according to the circuit diagram of Figure B.4 in Appendix B. Use a 680 Ω resistor for the adjustment resistor R. When complete, measure and record the source current iS with the DMM ammeter and confirm that it is close to 1.84 mA.
  2. Measure the value of the vout with the DMM voltmeter.
  3. Replace R2 with a 10 kΩ potentiometer. Monitor vout and adjust the potentiometer until the voltage reaches the specified limit. Disconnect the potentiometer from the circuit and then measure its resistance with the DMM ohmmeter.

Additional helpful tips for this section:

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