Another important difference between the VFB Op Amp and the CFB Op Amp is in the inherent relationship between gain and bandwidth. The VFB produces a constant gain times bandwidth product as diagramed in the left-hand figure. If the external circuit is configured for a gain of 100, for example, the maximum frequency for which the circuit will faithfully reproduce a sine wave input is 1/100th of the frequency, such that an input signal will be faithfully reproduced if the external configuration is for a gain of one. This relationship is easily remembered as the gain-bandwidth product for the IC. The point of inflection for an Op Amp is very low, on the order of a few hertz for low frequency VFB Op Amps and in the range of five to 10 kilohertz for high-speed VFB amplifiers. That’s referring to that dominant pole shown on the left-hand side of your figure. The slope of the gain-bandwidth product is the familiar one pole roll-off or six db per octave or 20 db per decade that we all know. In the case of the CFB Op Amp, the gain setting is based upon the external components and is independent of the frequency over the meaningful range of the operation of the CFB. Beyond the commencement of roll-off at point fA, the CFB amplifier exhibits the frequency attenuation characteristics of the VFB. This relationship allows for increased performance in terms of distortion and bandwidth per milliamp of supply current at high frequencies. The CFB amplifier is less flexible, however, in terms of external components than is the VFB amplifier. This will be seen in the limitations on the selection of the feedback resistor, RF, as will be discussed in the next foils.