3-28Figure 3-19.—Closed-loop frequency-response curve for gain of 10.The relationship between circuit gain and bandwidth in an operational-amplifier circuit can beexpressed by the GAIN-BANDWIDTH PRODUCT (GAIN BANDWIDTH = UNITY GAIN POINT).In other words, for operational-amplifier circuits, the gain times the bandwidth for one configuration of anoperational amplifier will equal the gain times the bandwidth for any other configuration of the sameoperational amplifier. In other words, when the gain of an operational-amplifier circuit is changed (bychanging the value of feedback or input resistors), the bandwidth also changes. But the gain times thebandwidth of the first configuration will equal the gain times the bandwidth of the second configuration.The following example should help you to understand this concept.The frequency-response curves shown in figures 3-17, 3-18, and 3-19 have a gain-bandwidth productof 1,000,000. In figure 3-17, the gain is 100,000 and the bandwidth is 10 hertz. The gain-bandwidthproduct is 100,000 times 10 (Hz), or 1,000,000. In figure 3-18, the gain has been reduced to 100 and thebandwidth increases to 10 kilohertz. The gain-bandwidth product is 100 times 10,000 (Hz) which is alsoequal to 1,000,000. In figure 3-19 the gain has been reduced to 10 and the bandwidth is 100 kilohertz. Thegain-bandwidth product is 10 times 100,000 (Hz), which is 1,000,000. If the gain were reduced to 1, thebandwidth would be 1 megahertz (which is shown on the frequency-response curve as the unity-gainpoint) and the gain-bandwidth product would still be 1,000,000.Q-19.What does the term "closed-loop" mean in the closed-loop configuration of an operationalamplifier?In answering Q20, Q21, and Q23, select the correct response from the choices given in theparentheses.

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