SBOU006 datasheet(13/33 Pages) TI2

13 / 33 page

OPA3691

www.ti.com

SBOS227E

TRIPLE ADC BUFFER CHANNEL

The OPAx691 family is ideally suited to single-supply,

wideband ADC driving. A current-feedback op amp is ideal

where high gains with high bandwidths are required. The

wide 3Vp-p output swing with over 150MHz full-power band-

width on a single +5V supply is well suited to the

2Vp-p input range commonly required from modern CMOS

pipelined ADCs. Three channels of very high-speed digitizer

channels are shown in Figure 3 using the OPA3691 driving

three ADS831s (8-bit, 80MSPS CMOS converters). Each

input is AC-coupled into a 50

Ω gain resistor that also will act

as a 50

Ω impedance match at high frequencies. The amplifier’s

inputs and outputs are centered on the ADC common-mode

input voltage by tying each converter’s VCM to the noninverting

inputs of the amplifier. This VCM acts as the swing midpoint

for the input to the converter. Since the ADS831 can operate

with differential inputs, driving into the IN input will give a net

noninverting signal channel even with the amplifiers operat-

ing at an inverting gain of –6. The other input to the ADS831

is tied to this VCM as well to give an input signal midpoint

equal to VCM. The 300Ω feedback resistor will be the output

load in this configuration. Harmonic distortion for the OPA3691

will not degrade the converter’s SFDR performance in this

application.

WIDEBAND RGB MULTIPLEXER

The OPA3691 is ideally suited to implementing a simple,

very wideband, 2x1 RGB multiplexer. This simple

wired-OR

video multiplexer can be easily implemented using the circuit

shown in Figure 4.

This circuit uses two OPA3691s where each package accepts

the three RGB component video signals from one of two

possible sources. Each noninverting input is terminated in 75

Ω

FIGURE 4. Wideband 2x1 RGB Multiplexer.

FIGURE 3. Triple-Channel ADC Driver.

1/3

OPA3691

Ω

300

Ω

0.1

µF

300

Ω

0.1

µF

47pF

ADS831

8-Bit

80MSPS

1/3

OPA3691

Ω

300

Ω

0.1

µF

300

Ω

0.1

µF

47pF

ADS831

8-Bit

80MSPS

1/3

OPA3691

Ω

300

Ω

0.1

µF

300

Ω

0.1

µF

47pF

ADS831

8-Bit

80MSPS

+5V

Power-supply

decoupling not shown.

1/3

OPA3691

340

Ω

402

Ω

82.5

Ω

OUT Red

Ω Line

+5V

–5V

1/3

OPA3691

340

Ω

402

Ω

82.5

Ω

OUT Green

Ω Line

1/3

OPA3691

340

Ω

402

Ω

82.5

Ω

OUT Blue

Ω Line

1/3

OPA3691

340

Ω

402

Ω

82.5

Ω

+5V

–5V

1/3

OPA3691

340

Ω

402

Ω

82.5

Ω

1/3

OPA3691

340

Ω

402

Ω

82.5

Ω

DIS

Power-supply

decoupling not shown.

SBOU006 bảng dữ liệu(PDF) 13 Page - Texas Instruments

SBOU006 bảng dữ liệu(HTML) 13 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33

bảng dữ liệu tải về

Link URL