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.