These are some of the more common line rates in use today. As it can be seen from this chart, at higher line rates, the bandwidth and slew rate requirements on the Op Amp could be demanding. When used in a gain of +2 configuration amplifying and buffering a video signal, the amplifier output could see voltage excursions of up to 1.4 volt peak-to-peak. In every case shown here, it is assumed that the video could take as long as one-third the total pixel time in order to reach the final voltage. Another one-third is for keeping the pixel potential and the last one-third for reverting back to the original voltage level. Obviously, the worst case would be alternate white and black

pixels or on and off pixels. Assuming a single pole roll-off, the amplifier speed can be effectively related to the sine wave concept of bandwidth through the expression “bandwidth is equal to .35 divided by rise or fall time”. Even though most systems are not exactly single-pole, this relationship is a good approximation. The term rise time is generally reserved for small signal and it refers to the time it takes the signal to travel between 10% and 90% of the final voltages. Generally speaking, an amplifier rise time would start to deteriorate as the amplitude is increased if the slew rate required is larger than what the amplifier is capable of. In a voltage feedback Op Amp, this is generally set by the amount of current available to charge the internal dominant pole capacitor as we have already seen in the previous foil. We can use the small signal rise time number to arrive at the amplifier slew rate because we know the total voltage swing to be around 1.4 volt peak-to-peak.