CLC411AMC datasheet(4/8 Pages) NSC

4 / 8 page

Description

The CLC411 is a high-speed current-feedback operational

amplifier which operates from ±15V power supplies.

The external supplies (±VCC) are regulated to lower

voltages internally. The amplifier itself sees

approximately ±6.5V rails. Thus the device yields

performance comparable to Comlinear’s ±5V devices,

but with higher supply voltages. There is no degradation

in rated specifications when the CLC411 is operated

from ±12V. A slight reduction in bandwidth will be

observed with ±10V supplies. Operation at less than

±10V is not recommended.

A block diagram of the amplifier and regulator topology

is shown in Figure 2, “CLC411 Equivalent Circuit.” The

regulators derive their reference voltage from an internal

floating zener voltage source. External control of the

zener reference pins can be used to level-shift amplifier

operation which is discussed in detail in the section

entitled “Extending Input/Output Range with Vr.”

Power Supply Decoupling

There are four pins associated with the power supplies.

The VCC pins (4,7) are the external supply voltages. The

Vr pins (5,1) are connected to internal reference nodes.

Figures 1 and 3 , “Recommended Non-inverting Gain

Circuit” and "Recommended Inverting Gain Circuit"

show the recommended supply decoupling scheme

with four ceramic and two electrolytic capacitors. The

ceramic capacitors must be placed immediately adjacent

to the device pins and connected directly to a good

0.01

µF

0.1

µF

0.1

µF

6.8

µF

6.8

µF

0.01

µF

-V

CLC411

out

DIS

-V

0.01

µF

0.1

µF

0.1

µF

6.8

µF

6.8

µF

0.01

µF

-V

CLC411

Ω

Select R

to yield

in =RT||Rg

out

DIS

-V

Figure 3: Recommended

Inverting Gain Circuit

Figure 1: Recommended

Non-inverting Gain Circuit

low-inductance ground plane. Bypassing the Vr pins will

reduce high frequency noise (>10MHz) in the amplifier.

If this noise is not a concern these capacitors may be

eliminated.

Differential Gain and Phase

The differential gain and phase errors of the CLC411

driving one doubly-terminated video load (RL=150

Ω) are

specified and guaranteed in the “Electrical

Characteristics” table. The “Typical Performance” plot,

“Differential Gain and Phase (4.43MHz)” shows the

differential gain and phase performance of the CLC411

when driving from one to four video loads. Application

note OA-08, “Differential Gain and Phase for Composite

Video Systems,” describes in detail the techniques

used to measure differential gain and phase.

Feedback Resistor

The loop gain and frequency response for a current-

feedback operational amplifier is determined largely by

the feedback resistor, Rf. The electrical characteristics

and typical performance plots contained within the

datasheet, unless otherwise stated, specify an Rf of

301

Ω, a gain of +2V/V and operation with ±15V power

supplies. The frequency response at different gain

settings and supply voltages can be optimized by

selecting a different value of Rf. Generally, lowering Rf

will peak the frequency response and extend the

bandwidth while increasing its value will roll off the

response. For unity-gain voltage follower circuits, a

Figure 4: Recommended Rf vs. Gain

Figure 2: CLC411 Equivalent Circuit

17k

Ω

17k

Ω

+Vcc

+Vr

-Vr

-Vcc

reg

http://www.national.com

Gain (V/V)

500

400

300

200

100

0123

Non-Inverting

Inverting

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