In a voltage feedback amplifier or VFB, the user is free essentially to choose the value of the feedback resistor. However, for video, as well as any other high-speed, high performance system, the higher order effects limit this selection. The amplifier, PC board layout, and individual components around the Op Amp have inherent parasitic capacitances of which the input capacitance on the inverting input is shown here. In a video amplifier in a gain of +2 configuration with input terminated in 75 ohms, the inverting node capacitance is the one which dictates the maximum on RF and RG values. In the case shown, the input capacitance, or CIN, will form a pole in the feedback. This pole is given by the expression shown and will have a tendency to increase the phase shift around the loop. With a typical input capacitance of around three pF using 2 kilo ohms for RF and RG, will result in this pole to be at around 53 megahertz. So, if the amplifier in use has a gain bandwidth product larger than 100 megahertz, it will have a phase margin less than 45 degrees. The result is that the overall amplifier will be less stable and tends to have overshoot in the time domain and frequency response peaking. Therefore, it’s best to keep the value of resistors low to the point that for a given application, no significant poles are introduced to get the cleanest frequency response.