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TA0310

Analog video formats

capacitance on the order of pF. In this situation, the driver must maintain high stability even under

capacitive loads. Set-top boxes can also feature an analog video input featuring the same constraints.

The choice of the video source is done via the set-top box. The source signal can be delivered from a

DVD or a video camera, for example.

The amplifier can be very specific, including features such as buffer+filtering (ex: STv6433) or video

matrix (STv6412), or, linked to the market trend, it can be embedded in the chipset.

On the other hand, the amplifier stage can also be a discrete solution using transistors or high-speed op-

amps. Where the customer’s goals are speed and space-saving, high-speed op-amps provide an

advantage as compared to a transistor solution. For this reason, there is currently a market for the high-

speed op-amps in broadcast video applications.

4 Analog video formats

The format of the analog video signal is very important in order to evaluate the frequency and amplitude

contraints required of the high-speed op-amp. There are three main division of signal formats, each

giving a different quality of television image.

The first type of signal format is comprised of three separate signals based on the R,G and B signals. This

signal form is the "purest" video signal, providing the highest quality image. The three R, B and G signals

feature the same bandwidth. This bandwidth is directly linked to the video resolution. In standard video

broadcast, we use commonly YIQ, YUV or YPbPr, where appears the Luma (Y), (I,U,Pb) and (Q,V,Pr) are

a component of R, B and Y. In of all these formats, three signals are driven.

The second type of signal format is based on two signals, such as Luma-Chroma (Y/C) or S-Video, where

C is the Chroma. Both are a coding of RGB signals linked to the NTSC, PAL and SECAM video standards

developed in the USA, Europe and Asia.

Figure 1: Location of op-amps in video applications

DVD

Set-Top-Box

CAMERA

SCART PLUGs

output

output

input

output

TV

Terrestrial

Cable

Satellite

Cable

Satellite

150

Ω Load

75

Ω line

75

Ω line

75

Ω line

75

Ω line

150

Ω Load

150

Ω Load

Capa Load

Capa Load

Capa Load

input

input