OPA623AP datasheet(9/16 Pages) TI1

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OPA623

DISCUSSION OF

PERFORMANCE

Requiring very low quiescent power, the OPA623 achieves

its exceptional AC performance by using the current-feed-

back topology. This wide-band monolithic operational am-

plifier is designed for gain applications of up to 20V/V,

where power and cost are of primary concern.

Operating from a

±5V supply, the OPA623 consumes only

40mW, yet maintains a 350MHz large-signal bandwidth at

OUT = 2.8Vp-p and a 2100V/µs slew rate. Benefiting

from the current-feedback architecture, the OPA623 offers

stable operation with no compensation capacitor, even at

unity gain.

With its low differential gain and phase errors of typically

0.12% and 0.05

° at 4.43MHz, the OPA623 meets the perfor-

mance and cost requirements of high-volume broadcast and

HDTV applications.

The OPA623’s large-signal bandwidth, high slew rate,

excellent pulse response, and high drive capabilities are

features well-suited to wide-band RGB video applica-

tions, RF instruments, and even high-speed digital com-

munication systems.

For most circuit configurations, the OPA623 current-

feedback op amp can be treated like a conventional op

amp. As with a voltage-feedback op amp, the feedback

network connected to the inverting input controls the

closed-loop gain. But with a current-feedback op amp, the

impedance of the feedback network also controls the

open-loop gain and frequency response. Feedback resis-

tor values can be selected to provide nearly constant

closed-loop bandwidth over a wide range of gains and flat

gain adjustment vs frequency.

DESCRIPTION

A wide-band operational transconductance amplifier (OTA)

and an output buffer are the main blocks of a current-

feedback op amp. The simplified circuit diagram is illus-

trated in Figure 2. The OTA consists of a complementary

unity-gain amplifier and a subsequent current mirror. The

input buffer is connected across the inputs of the op amp.

The voltage at the high-impedance +In terminal is trans-

ferred to the –In terminal at a low impedance. The current

mirrors reflect any current flowing into or out of the +In

terminal by a fixed ratio to the high-impedance OTA output,

which is directly connected to the complementary output

buffer. It is designed to drive low-impedance transmission

FIGURE 2. Simplified Circuit Diagram.

+In

OUT

–V

CC = –5V

CC = +5V

OTA

BUFFER

Bias

Circuitry

–In

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