OPA684

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Copyright © 2001, Texas Instruments Incorporated

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of

Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

SBOS219A – MARCH 2002

Low-Power, Current Feedback

OPERATIONAL AMPLIFIER With Disable

FEATURES

q MINIMAL BANDWIDTH CHANGE VERSUS GAIN

q > 120MHz BANDWIDTH TO GAIN > +10

q LOW DISTORTION: < –78dBc at 5MHz

q HIGH OUTPUT CURRENT: 120mA

q SINGLE +5V TO +12V SUPPLY OPERATION

q DUAL

q LOW SUPPLY CURRENT: 1.7mA

q LOW SHUTDOWN CURRENT: 100

V+

V

O

V–

I

ERR

R

G

R

F

Z

+

Low-Power

Amplifier

DESCRIPTION

The OPA684 provides a new level of performance in low-power,

fier is the first to use an internally closed-loop input buffer stage that

enhances performance significantly over earlier low-power CFB

amplifiers. While retaining the benefits of very low power operation,

this new architecture provides many of the benefits of a more ideal

CFB amplifier. The closed-loop input stage buffer gives a very low

and linearized impedance path at the inverting input to sense the

feedback error current. This improved inverting input impedance

retains exceptional bandwidth to much higher gains and improves

harmonic distortion over earlier solutions limited by inverting input

amplifier permits the gain setting element to be set with consider-

able freedom from amplifier bandwidth interaction. This allows

frequency response peaking elements to be added, multiple input

inverting summing circuits to have greater bandwidth, and low-

OPA684

OPA684

APPLICATIONS

q LOW-POWER BROADCAST VIDEO DRIVERS

q EQUALIZING FILTERS

q SAW FILTER HIGH GAIN POST AMPLIFIERS

q MULTICHANNEL SUMMING AMPLIFIERS

q PROFESSIONAL CAMERAS

q ADC INPUT DRIVERS

power line drivers to meet the demanding requirements of studio

cameras and broadcast video.

The output capability of the OPA684 also sets a new mark in

performance for low-power current feedback amplifiers. Delivering

a full

±4Vp-p swing on ±5V supplies, the OPA684 also has the

output current to support this swing into a 100

Ω load. This minimal

output headroom requirement is complemented by a similar 1.2V

input stage headroom giving exceptional capability for single +5V

operation.

The OPA684’s low 1.7mA supply current is precisely trimmed at

25

°C. This trim, along with low shift over temperature and supply

voltage, gives a very robust design over a wide range of operating

conditions. System power may be further reduced by using the

optional disable control pin. Leaving this disable pin open, or holding

it HIGH, gives normal operation. If pulled LOW, the OPA684 supply

current drops to less than 100

µA while the I/O pins go to a high

impedance state.

3

0

–3

–6

–9

–12

–15

–18

–21

R

G = 100

G = 50

G = 20

G = 10

G = 5

G = 2

10

100

200

BW (MHz) vs GAIN

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of Texas Instruments

standard warranty. Production processing does not necessarily include

testing of all parameters.

Patent Pending