FEATURES

MINIMAL BANDWIDTH CHANGE VERSUS GAIN

> 120MHz BANDWIDTH TO GAIN > +10

LOW DISTORTION: < –78dBc at 5MHz

HIGH OUTPUT CURRENT: 120mA

SINGLE +5V TO +12V SUPPLY OPERATION

DUAL ±2.5 TO ±6.0V SUPPLY OPERATION

LOW SUPPLY CURRENT: 1.7mA

LOW SHUTDOWN CURRENT: 100μA

APPLICATIONS

LOW-POWER BROADCAST VIDEO DRIVERS

EQUALIZING FILTERS

SAW FILTER HIGH GAIN POST AMPLIFIERS

MULTICHANNEL SUMMING AMPLIFIERS

PROFESSIONAL CAMERAS

ADC INPUT DRIVERS

DESCRIPTION

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

wideband, current-feedback (CFB) amplifiers. This CFBplus amplifier

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

linearity. Beyond simple high-gain applications, the OPA684 CFBplus

amplifier permits the gain setting element to be set with considerable

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-

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 ±4VPP swing on ±5V supplies, the OPA684 also has the

output current to support this swing into a 100Ω 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 100μA while the I/O pins go to a high

impedance state.