OPA361-Q1 Datasheet, PDF (10/18 Pages) Texas Instruments – 3V Video Amplifier with Internal Gain and Filter in SC70

OPA361-Q1
SBOS552 – MARCH 2011
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Figure 5. Multiburst Signal (CCIR 18/1) Shows Very Flat Frequency Response
The CCIR17 test pattern contains a 2T and a 20T pulse, as shown in Figure 6. The 2T pulse is used to check for
pulse distortion and reflection, and the 20T pulse is used to check for amplitude and group delay between
chrominance and luminance. Neither pulse exhibits any distortion or group delay artifacts.
Figure 6. CCIR 17 2T and 20T Pulses Show No Visible Distortion
INTERNAL LEVEL SHIFT
Many common video DACs embedded in digital media processors, like the new OMAP242x processors, operate
on a single supply (no negative supply). Typically, the lowest point of the sync pulse output by these video DACs
is close to 0V. With a 0V input, the output of a common single-supply op amp saturates at a voltage > 0V. This
effect would clip the sync pulse, and therefore degrade the video signal integrity. The OPA361-Q1 employs an
internal level shift circuit to avoid clipping. The input signal is typically shifted by approximately 11mV. This shift
is well within the linear output voltage range of the OPA361-Q1 with a standard 150Ω video load.
Output Swing Capability
Figure 7 shows the true output swing capability of the OPA361-Q1 by taking the tip of the input sync pulse to a
slightly negative voltage. Even when the output sync tip is at 3mV, the output after the 75Ω series termination still
shows no clipping of the sync pulse.
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