Diagram Diagosis

The FMS6363 Low Cost Video Filter (LCVF) provides 6dB gain from input to  output. In addition, the input will be slightly offset to optimize the output driver performance. The FMS6363 provides an internal diode clamp to support AC-coupled input signals. If the input signal does not go below ground, the input clamp will not operate. This allows DAC outputs to directly drive the FMS6363 without and AC coupling capacitor (usually 220 ?F). The offset is held to the minimum required value to decrease the standing DC current into the load.

The circuit diagram shows a low-cost 3-input video MUX cable driver. In this circuit, the amplifier is loaded by the sum of RF and RG of each disabled amplifier. Resistor values have been chosen to keep the total back termination at 75 Ω while maintaining a gain of 1 at the 75-Ω load. The switching time between any two channels is approximately 32 ns when both enable pins are driven. When designing a circuit board for this cable driver, care should be taken to minimize trace lengths at the inverting input. The ground plane should also be pulled away from RF and RG on both sides of the board to minimize stray capacitance. Current consumption of the cable driver is a modest 8mA.