FEATURES
MINIMAL BANDWIDTH CHANGE VERSUS GAIN
170MHz BANDWIDTH AT G = +2
> 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/ch

APPLICATIONS
LOW-POWER BROADCAST VIDEO DRIVERS
EQUALIZING FILTERS
SAW FILTER HIGH-GAIN POST AMPLIFIERS
MULTICHANNEL SUMMING AMPLIFIERS
WIDEBAND DIFFERENTIAL CHANNELS
ANALOG-TO-DIGITAL CONVERTERS INPUT
DRIVERS
MULTIPLE POLE ACTIVE FILTERS
OPA4658 LOW-POWER UPGRADE

DESCRIPTION
The OPA4684 provides a new level of performance in lowpower,
wideband, current-feedback (CFB) amplifiers. This
CFBPLUS amplifier is among the first to use an internally
closed-loop input buffer stage that enhances performance
significantly over earlier low-power CFB amplifiers. This new
architecture provides many of the benefits of a more ideal
CFB amplifier while retaining the benefits of very low power
operation. 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 OPA4684 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 OPA4684 also sets a new mark
in performance for low-power current-feedback amplifiers.
Delivering a full ±4VPP swing on ±5V supplies, the OPA4684
also has the output current to support > ±3V swing 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 OPA4684’s low 6.8mA 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.