OPA358 datasheet(10/18 Pages) TI2

10 / 18 page

OPA358

SB0S296C − MARCH 2004 − REVISED FEBRUARY 2005

www.ti.com

The output voltage swing for the circuit with sag correction

(see Figure 7b) is a function of the coupling capacitor

value. The value of the sag correction capacitor has only

a minor influence. The smaller the coupling capacitor, the

greater the output swing. Therefore, to accommodate the

large signal swing with very small coupling capacitors

(22

µF and 33µF), a higher supply voltage might be

needed.

DC-COUPLED OUTPUT

Due to the excellent swing to ground, the OPA358 can also

be DC- coupled to a video load. As shown in Figure 8, this

eliminates the need for AC-coupling capacitors at the

output. This is especially important in portable video

applications where board space is restricted.

The DC-coupled output configuration also shows the best

video performance. There is no line or field tilt—allowing

use of the lowest power supply. In this mode, the OPA358

will safely operate down to 2.5V with no clipping of the

signal.

The disadvantage with DC-coupled output is that it uses

somewhat higher supply current.

WIDEBAND VIDEO MULTIPLEXING

One common application for video amplifiers which

include an enable pin is to wire multiple amplifier outputs

together, then select which one of several possible video

inputs to source onto a single line. This simple Wired-OR

Video Multiplexer can be easily implemented using the

OPA358, as shown in Figure 9.

OUT

Ω

V+ = 2.7V to 3.3V

Enable

(1)

Video

DAC

NOTE: (1) Optional 200

Ωfor use with TI’s digital media processors,

and 500

Ωfor OMAP2420 and OMAP2430 processors.

Ω

Television

or VCR

OPA358

GND

G= 1 +

Figure 8. DC-Coupled Input/DC-Coupled Output

Ω

OPA358

+3.3

µF

10nF

Ω

OUT

Ω

Signal #1

Ω

HCO4

OPA358

+3.3V

µF

10nF

Ω

Signal #2

Select

Ω

Figure 9. Multiplexed Output

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