Q. What are frequency response curves? How are they made?

Every amplifier has a frequency-response curve associated with it. They provide a "picture" of the performance of an amplifier at various frequencies. The amplifier for which the frequency-response curve is created is tested at various frequencies. At each frequency, the input signal is set to some predetermined level of voltage (or current). This same voltage (or current) level for all of the input signals is used to provide a standard input and to allow evaluation of the output of the circuit at each of the frequencies tested. For each of these frequencies, the output is measured and marked on a graph. The graph is marked "frequency" along the horizontal axis and "voltage" or "current" along the vertical axis. When points have been plotted for all of the frequencies tested, the points are connected to form the frequency- response curve. The shape of the curve represents the frequency response of the amplifier.