• Know what the terminals of an op amp are, what they are used for, and what symbols are used for their voltage and current variables.
• Know what the circuit symbol for an op amp without power supply terminals is and what the constraint is on the voltages and currents of the input terminals.
• Know how to connect an op amp and two resistors to develop an inverting or non-inverting amplifier circuit, and be able to calculate the amplifier gain. Know the difference between open-loop gain and closed-loop gain.
• Know how to connect an op amp and resistors to provide a summing function.
• Know how to connect an op amp and three resistors to develop a differencing circuit, and be able to calculate the scaling factors for each of the input voltages.
• Know what is meant by the common mode rejection ratio, and how it is used as a measure of difference amplifier performance.
• Know how the basic ideal op amp circuit model can be extended to include finite input resistance and nonzero output resistance.

Skills: In studying the material in this chapter, you should make certain that you develop the following skills:

• Be able to analyze an ideal op amp circuit by taking account of the constraints on the voltage and current input variables.
• Be able to analyze the range of input voltages to an op amp circuit to make certain that saturation does not occur.
• Be able to design resistor networks which when connected to an op amp will provide inverting, non-inverting, summing and differencing functions.
• Be able to evaluate a differencing op amp circuit for differential mode gain and common mode gain and calculate the common mode rejection ratio.
• Be able to determine the effect of non-infinite input and non-zero output resistance on the performance of inverting and non-inverting op amp circuits.

Review Questions: Test your understanding of the material in this chapter by answering the following review questions:

1. Since the gain of op amp circuits is determined by the ratio of resistors, rather than their absolute values, what are the factors that determine the choice of absolute resistor values?

2. Evaluate the performance of an inverting amplifier op amp circuit as the absolute resistor values are changed (for a fixed gain value) using both ideal and non-ideal op amp models.

3. Repeat question 2 for a non-inverting amplifier circuit.

4. In the non-inverting amplifier circuit, what is the result of setting the feedback resistor to a zero value. Can you suggest some uses for such a circuit?