7

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following equation:

SR

peak

The slew rate of the CLC418 in inverting gains is always

higher than in non-inverting gains.

AC Design (linear phase/constant group delay)

and a reasonably linear phase response. To improve

50% over its recommended value. Some adjustment of

application. See the

AC Design (small signal band-

Propagation delay is approximately equal to group delay.

Group delay is related to phase by this equation:

where

φ(f) is the phase in degrees. Linear phase implies

constant group delay. The technique for achieving linear

phase also produces a constant group delay.

AC Design (peaking)

Peaking is sometimes observed with the recommended

then investigate the possible causes and remedies

listed below:

s

s

s

Use a resistor with low parasitic

s

A capacitive load

s

Use a series resistor between the output

and a capacitive load (see the

Settling

s

and the CLC418

s

Keep these traces as short as possible

For non-inverting and transimpedance gain configurations:

s

Extra capacitance between the inverting

s

See the

Printed Circuit Board Layout

sub-section below for suggestions on

s

For inverting gain configurations:

s

Inadequate ground plane at the non-inverting

pin and/or long traces between non-inverting

pin and ground

s

Place a 50 to 200

Ω resistor between the

Figure 2)

AC Design (crosstalk)

Crosstalk performance depends on the layout.

Three

layout techniques that can reduce crosstalk are:

s

Provide short symmetrical ground return paths for:

s

the inputs

s

the supply bypass capacitors

s

the load

s

Provide a short, grounded guard trace that:

s

goes underneath the package

s

is 0.1” (3mm) from the package pins

s

is on top and bottom of the printed circuit

board with connecting vias

s

Try different bypass capacitors to reduce high

frequency crosstalk

The CLC418’s evaluation board was used to produce the

Input-Referred Crosstalk plot.

Capacitive Loads

Capacitive loads, such as found in A/D converters,

settling performance. The

Settling Time vs. Capacitive

Load plot in the Typical Performance Characteristics

section provides the information for selecting this resistor.

Using a resistor in series with a reactive load will also

reduce the load’s effect on amplifier loop dynamics. For

instance, driving coaxial cables without an output series

resistor may cause peaking or oscillation.

Transmission Line Matching

One method for matching the characteristic impedance

of a transmission line is to place the appropriate

resistor at the input or output of the amplifier. Figure 6

shows the typical circuit configurations for matching

transmission lines.

Figure 6: Transmission Line Matching

transmission line or cable.

amplifier from reactive loading caused by the transmis-

sion line, or by parasitics.

The input and output matching resistors attenuate the

signal by a factor of 2, therefore additional gain is needed.

frequency range.

It compensates for the increase of

the op amps output impedance with frequency.

τ

φ

φ

gd

d

d

f

1

360

f

f

1

360

f

f

°

⋅

( )

≈ −

°

⋅

( )

∆

∆

+

-

418 Fig6

+

-

1/2

CLC418