Five new operational amplifiers (op-amps) from Fairchild allow designers to target a broad range of high definition (HD) and standard definition (SD) video applications including set-top boxes, digital TVs and audio/video amplifiers. Designed-in properly, the 210MHz FHP3x50 and the 50MHz FHP3x30 families go a long way to meeting dual objectives of delivering superior amplifier performance whilst maintaining very low power consumption.
The triple- and quad-channel FHP3x50 devices offer 210MHz full-power bandwidth (-3dB), exceed HD video requirements and deliver 1100V/µs slew rate for optimal pulse response. In addition, the devices’ 0.07%/0.03 degree differential gain/phase error improves video quality.
A gain flatness of 0.1dB (50MHz) enables them to maintain consistent gain over the entire passband of high-definition video signals. DC accuracy is also improved thanks to 0.05µA typical input bias-current, which allows for more precise output-voltage levels and minimal droop in AC-coupled applications.
Both devices in the 210MHz family require just 3.6mA supply current per amplifier, with the triple-channel device offering a disable feature to prevent additional power consumption. This, combined with an output current rating of +/-55mA, makes these devices ideal for driving multiple video loads. The FHP3x50 ICs are also well suited for use in DTVs, audio/video (A/V) amps and projectors and DVD recorders.
The single-, dual- and quad-channel devices in the FHP3x30 family provide 50MHz bandwidth, 110V/µs slew rate and 0.008% /0.01 degree differential gain/phase to improve performance in SD video designs. Key performance figures for the FHP3x30 devices include 170MHz bandwidth, 100mA output current and a CMRR of 100dB. Typical power consumption is just 2.5mA. All three amplifiers offer superior gain flatness (16MHz to 0.1dB) to increase system reliability and simplify designs. Specifications such as these are crucial for applications including SD set-top boxes, DTVs, CCD imaging systems and industrial imaging systems.
The well rounded performance characteristics of these amplifiers make them well suited for many general purpose applications. The gain flatness and differential gain/phase performance make them well suited for SD, PS, or HD applications.
When driving a video load, usually a 75ohm coaxial cable, it is important to utilize a doubly terminated configuration similar to Figure 1. To ensure maximum stability and performance, it is important to use both a source termination resistor and an end termination resistor. When a 75ohm cable is used, make both termination resistors 75ohm. The termination resistors will attenuate the signal by a factor of 2 or 6dB. Set the amplifier’s gain to counter this effect. If a 1Vpp signal is applied to the input and 1Vpp is also desired at output of the cable, then set the amplifiers gain to 6dB or 2V/V.
Both the FHP3x30 and FHP3x50 family of amplifiers offer ample output current for driving long cable lengths or multiple video loads. The FHP3230 can easily drive four video loads, but having enough drive capability is not the only concern. As an amplifier drives multiple video loads, its differential gain and phase contribution increases. The usefulness of the extremely low differential gain and phase of the FHP3x30 family becomes evident as it drives more loads.