FEATURES

MINIMAL BANDWIDTH CHANGE VERSUS GAIN

170MHz BANDWIDTH: G = +2

> 120MHz BANDWIDTH TO GAIN > +10

LOW DISTORTION: < –82dBc at 5MHz

HIGH OUTPUT CURRENT: 120mA

SINGLE +5V TO +12V SUPPLY OPERATION

DUAL ±2.5V TO ±6.0V SUPPLY OPERATION

LOW SUPPLY CURRENT: 1.7mA/ch

LOW SHUTDOWN CURRENT: 100μA/ch

APPLICATIONS

RGB LINE DRIVERS

LOW-POWER BROADCAST VIDEO DRIVERS

EQUALIZING FILTERS

MULTICHANNEL SUMMING AMPLIFIERS

PROFESSIONAL CAMERAS

ADC INPUT DRIVERS

DESCRIPTION

The OPA3684 provides a new level of performance in low-power,

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

among the first to use an internally closed-loop input buffer

stage that enhances performance significantly over earlier lowpower

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 OPA3684 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 OPA3684 also sets a new mark in

performance for low-power current-feedback amplifiers. Delivering

a full ±4Vp-p swing on ±5V supplies, the OPA3684 also has the

output current to support > ±3Vp-p into 50Ω. This minimal output

headroom requirement is complemented by a similar 1.2V input

stage headroom giving exceptional capability for single +5V operation.

The OPA3684’s low 1.7mA/ch 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 OPA3684 supply

current drops to less than 100μA/ch while the I/O pins go to a high

impedance state.