EL2090CM, Elantec

EL2090CM, Intersil

100MHz DC-Restored Video Amplifier

he EL2090 is the first complete DC-restored monolithic video amplifiersub-system. It contains a very high-quality video amplifier and a nulling sample-and-holdamplifier specifically designed to stabilize videoperformance. When the HOLD logic input is set to a logic 0during a horizontal sync, the sample-and-hold amplifier maybe used as a general-purpose op-amp to null the DC offsetof the video amplifier. When the HOLD input goes to a logic1 the sample-and-hold stores the correction voltage on thehold capacitor to maintain DC correction during thesubsequent scan line.The video amplifier is optimized for video characteristics,and performance at NTSC is nearly perfect. It is a current-feedback amplifier, so that -3dB bandwidth changes little atvarious closed-loop gains. The amplifier easily drives videosignal levels into 75Ωloads. With 100MHz bandwidth, theEL2090 is also useful in HDTV applications.The sample-and-hold is optimized for fast sync pulseresponse. The application circuit shown will restore the videoDC level in five scan lines, even if the HOLD pulse is only2μs long. The output impedance of the sample-and-hold islow and constant over frequency and load current so that theperformance of the video amplifier is not compromised byconnections to the DC restore circuitry.The EL2090 is fabricated in Elantec’s proprietaryComplementary Bipolar process which produces NPN andPNP transistors with equivalent AC and DC performance.The EL2090 is specified for operation over the 0°C to 75°Ctemperature range.