Basic Low Output Impedance Multiplexer
Created: Aug 31, 2014
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Both inputs are terminated in their characteristic impedance; 75 Ω is typical for video applications. Because the output cables usually are terminated in their characteristic impedance, the gain is 0.5. Consequently, amplifiers U2A and U2B are configured in a gain of +2 to set the circuit gain at 1. R2 and R3 determine the amplifier gain; if a different gain is desired, R2 should be changed according to the equation G = (1 + R3/R2). R5, LCL1, and D1 make up an asymmetrical charge/discharge time circuit that configures U1 as a break-before-switch to prevent both amplifiers from being active simultaneously. The multiplexer transition time is approximately 15 µs with the component values shown.