Introduction
The circuit in Figure 1 transmits 200MHz (-3dB bandwidth) video signals while stripping off the sync pulse and performing DC restoration. It is configured for a typical video cable driver application driving a double-terminated 75Ω load, where the EL8102 (IC3) is configured for a gain of +2 to ensure unity gain throughout.
Sync Stripping
In component video systems it is frequently necessary to remove the sync pulse from an RGB signal. Sync is often combined with one or more of the red, green, and blue video signals in video distribution amplifiers, routers and switchers to decrease the number of input and output channels required in a switching network. In many applications, however, as the video signals exit the switching network the sync pulse must be removed.
The EL8102 video op amp is specially designed to perform sync stripping. Its open emitter NPN output forms an emitter-follower with the load resistor, and passes the active video signal while virtually eliminating the negative sync pulse (see Figure 2). Residual sync of the EL8102, defined as the remainder of the original -300mV sync pulse, referenced to ground, is only 8mV at the cable output. A particular advantage of sync stripping with the EL8102 is the resultant larger (by 0.7V) output voltage swing, compared to simply using a wideband video op amp with an external emitter-follower.