3-Input Video MUX Cable Driver Using LT1399


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.


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