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HIGH_PERFORMANCE_VIDEO_SWITCH

2016-09-13 04:59  
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HIGH_PERFORMANCE_VIDEO_SWITCH
This figure shows a one-of-two switch with a summing amplifier. The video source's line can be termi-nated either externally or internally to switch R0. With this termination resistor, a load change of less than 1 Ω will be seen by the source when the switch changes state. For this reason, input isolation amplifiers are not necessary. R4 can be varied to control circuit gain, but should never be less than 1400 Ω since the NE5539 is internally compensated for gain values greater than seven. A value of approximately 2500 Ω for R4 will set circuit gain to near unity. Additionally, the circuit output impedance is set by R6, and R5 sets the output dc offset to near zero.