Basic Op-amp Circuits: Comparator and Summing Amplifiers

This section identifies the use of positive feedback in op amp circuits. Analyze the operation of several basic comparator circuits and the operation of several types of summing amplifiers.


Key Concepts

  • Hysteresis
  • Schmitt trigger
  • Comparator
  • Summing amplifier
  • Digital-to-analog converter
  • Comparators operate with open-loop gain.
  • The output is limited by the power supply voltage applied to the circuit.
  • Noise levels are usually the same at both the inverting and non-inverting inputs.
  • An op amp comparator that uses hysteresis is called a Schmitt trigger.
  • Noise at the input of the comparator can cause inadvertent output transitions.
  • Hysteresis (positive feedback) is used to minimize the impact of noise on the comparator output.
  • A summing amplifier can be scaled to apply unity gain to all inputs.
  • A summing amplifier can be scaled to apply greater than unity gain to all inputs.
  • A summing amplifier can be scaled to apply differing gains to the inputs (scaling adder).
  • The use of negative feedback has a major impact on the input and output impedance that can be far different than the design parameters.
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