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.