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Topic 12 Op-Amp Applications

Topic 12 Op-Amp Applications. Comparators Integrators and Differentiators Summing Amplifiers Other Op-Amp Circuits Active Filters Low-Pass and High-Pass Band-Pass Filters. The op-amp provides a constant-current source for the capacitor, causing it to charge at a linear rate.

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Topic 12 Op-Amp Applications

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  1. Topic 12 Op-Amp Applications • Comparators • Integrators and Differentiators • Summing Amplifiers • Other Op-Amp Circuits • Active Filters • Low-Pass and High-Pass • Band-Pass Filters EDV255 0902 Op-Amp Applications

  2. The op-amp provides a constant-current source for the capacitor, causing it to charge at a linear rate. Op-Amp Integrator EDV255 0902 Op-Amp Applications

  3. A feedback resistor limits the gain at low frequency since the reactance of Cf increases, causing an increase in voltage gain. • Any output offset voltage can also be reduced. Reduced Gain Op-Amp Integrator Rf is normally >= 10 Rin EDV255 0902 Op-Amp Applications

  4. Differentiator – A circuit whose output is proportional to the rate of change of its input signal. 12.2.2 Differentiator EDV255 0902 Op-Amp Applications

  5. The added Rin resistor limits the gain at high frequency since the reactance of Cf is extremely low at higher frequencies Reduced Gain Op-Amp Differentiator EDV255 0902 Op-Amp Applications

  6. Summing amplifier– An op-amp circuit that produces an output proportional to the sum of its input voltages. 12.3 – Summing Amplifiers EDV255 0902 Op-Amp Applications

  7. Example 16.4: Determine the output voltage. Summing Amplifiers Example (1) Solution: Voltage gain equals -1 for all the inputs. EDV255 0902 Op-Amp Applications (-1)(3V + 6V + 4V) = -13V

  8. Example 16.5: Determine the output voltage. Summing Amplifiers Example (2) Solution: Voltage gain equals -0.1 for all the inputs. EDV255 0902 Op-Amp Applications (-0.1)(10V+8V+7V) = -2.5V

  9. General-class equation– An equation derived for a summing amplifier that is used to predict the circuit output for any combination of input voltages. • Determine the Rf / R ratio for each branch. • Represent each branch as the product of its resistance ratio and input voltage. • Write the equation as the sum of these products. General Summing Circuits EDV255 0902 Op-Amp Applications

  10. Example 16.6: Determine the output voltage for the 3 sets of inputs. Summing Amplifiers Example (3) Solution: EDV255 0902 Op-Amp Applications

  11. One summing amplifier application is as a digital-to-analog (D/A) converter. • Digital-to-analog (D/A) converter– A circuit that converts digital circuit outputs to equivalent analog voltages. Simplified D/A Converter EDV255 0902 Op-Amp Applications

  12. By using the proper input and feedback resistors, a summing amplifier can be an averaging amplifier. • Averaging amplifier– A summing amplifier that provides an output proportional to the average of the input voltages. Averaging Amplifier EDV255 0902 Op-Amp Applications

  13. Difference amplifier– A summing amplifier that provides an output proportional to the difference between two input voltages. Also called a subtractor. Difference Amplifier (Subtractor) In order to work properly, a difference amplifier must have values of R1 = R2 and R3 = R4 EDV255 0902 Op-Amp Applications

  14. Instrumentation amplifier– A high-gain and high-CMRR circuit used to amplify low-level signals in process control and measurement applications. 12.4 – Other Op-Amp Circuits EDV255 0902 Op-Amp Applications

  15. Audio amplifier– The final audio stage in low-power communications receivers, used to drive the speakers. Audio Amplifier EDV255 0902 Op-Amp Applications

  16. Voltage-Controlled Current Source • Voltage-controlled current source– A circuit with a constant-current output controlled by the circuit input voltage. EDV255 0902 Op-Amp Applications

  17. Precision rectifier– A clipper that consists of a diode and an op-amp. The circuit can clip extremely low- Precision Rectifier level input signals. EDV255 0902 Op-Amp Applications

  18. Op-Amp Applications (1) • A comparator is a circuit used to compare two voltages. • Most comparators use a voltage-divider to set the reference voltage. • An op-amp integrator provides a linear/ramp output waveform with a square-wave input. • A differentiator is a circuit whose output is proportional to the rate of change of its input signal. • A summing amplifier produces an output proportional to the sum of its input voltages. • A averaging amplifier provides an output proportional to the average of the input voltages. • A difference amplifier (subtractor) provides an output proportional to the difference between two input voltages. • Chapter 16 Problems (min.): 1, 3, 5, 7, 11, 13, 15, 17, 19 EDV255 0902 Op-Amp Applications

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