To aid in the evaluation of the CLC440, CLC446, and
CLC449 series of wide bandwidth parts, National
Semiconductor has created the evaluation boards for the
8-pin DIP, SOIC, and MSOP respectively. All evaluation
boards are optimized for use with high quality surface-
mount resistors and capacitors for obtaining the best high
frequency response.

I. Basic Component Selection
The evaluation boards are laid out for a non-inverting
gain of 2V/V using low-parasitic surface-mount resistors
and capacitors. The CLC44X very high frequency
amplifiers can be sensitive to component parasitics
that may alter AC performance especially in the high
frequency domain. Small adjustments in R

and/or R. are

recommended to shape the final desired frequency
response.

For CFB (the CLC446, and CLC449), increasing R

from

its recommended value will band limit the device's
frequency response, while decreasing Rf from its
recommended value will peak frequency response.
However, substantially decreasing the feedback resistor
of a current-feedback amp from its recommended value
may cause a part to oscillate. Application note OA-13
"Current-Feedback Amplifier Loop-Gain Analysis and
Performance Enhancements" of the data book elaborates
on the selection of feedback resistors and their influence
on AC performance.

For VFB (the CLC440), increasing both/either R

and R

from recommended values may cause high frequency
peaking. Decreasing both/either R

and R

may help

decrease high frequency peaking (without causing
oscillations).

II. Basic Connections & Operation
Both the DIP and SOIC evaluation boards provide for
input and output signal connections through SMA
connectors. These SMAs are connected to the non-
inverting input pin (pin 3) and the R

out

resistor as shown

in Figure 1. The recommended feedback resistor value
for the CLC44X series is 250

. The appropriate gain

setting resistor (R

) is calculated with Eq. 1.

The R

out

resistor, of Figure 1, should always be inserted

between pin 6 and the output SMA when driving coaxial
cable or capacitive loads. The plot in the typical
performance section labeled "Settling Time vs. Capacitive
Load" of the data sheets should be used to determine the
optimum resistor value for R

out

when driving coax or

capacitive loads. This optimal resistance improves settling
time for pulse-type applications and increases stability.

Figure 1: Schematic for 73055/60/76 Eval. Boards

Although no DC trim network was included on the evaluation
board, OA-07 has specific circuits to correct DC offsets.

Power-supply bypassing capacitors perform a very
important function for the CLC44X series and should not
be omitted when evaluating these amplifiers. The bypass
capacitors not only provide a low impedance current path
at the supply pin, but also provide high frequency filtering
on the power supply traces. C1 and C2 of Figure 1
should be quality 6.8

�

F tantalum capacitors. C3 and C4

should be quality 0.01

�

F ceramic capacitors. C4 and CS

should be quality 500pF ceramic capacitors.

The use of standard dip sockets is not recommended for
the CLC44X series DIP amplifiers. These sockets may
severely degrade AC performance and may cause oscil-
lations. The 730055 PDIP evaluation board will easily
accommodate flush-mount socket pins when socketing is
necessary. The printed circuit board device holes are sized
for Cambion P/N 450-2598 socket pins or their equivalent.

III. Printed Circuit Board Layout Considerations
The evaluation boards have been carefully laid out to
optimize the performance of the CLC44X series. The
ground plane on the evaluation boards was removed
near the sensitive nodes (pins 2, 3, 6) to reduce parasitic
capacitances between these nodes and the ground
plane. Trace lengths were also minimized to reduce
series inductances associated with all components and
all nodes.

The CLC44X series is sensitive to the parasitics on
traces. This sensitivity includes capacitive coupling
from trace to power and trace to ground planes. If
leaded components are used, then a low inductive
resistor supplied by Precision Resistor Products or its
equivalent is highly recommended. In all instances
surface-mount components are recommended over
leaded components.

CLC44X Evaluation Boards

Part Number CLC730055, CLC730060, CLC730076

August 1997

� 1997 National Semiconductor Corporation

http://www.national.com

Printed in the U.S.A.

Eq. 1

( for A

2 R

250 )

= +

IV. Measurement Hints
If 50

coax and 50

out

resistors are used, many of

the typical performance plots found in the data sheets for
the CLC44X's are reproducible.

When SMA connectors and cables are not available to
evaluate the CLC44X series, normal oscilloscope probes
should not be used. Alternatively low impedance probes,
of 100 to 500

, should be used. If a low impedance

probe is not available, then a section of 50

coaxial

cable and a low impedance resistor may be used.
Connect one end of coax's center to a test measurement
box terminated in 50

and the other end of the cable's

center conductor to the low impedance resistor. The
open side of the low impedance resistor is now a probe.
The ground shield of the cable should be connected to
evaluation board ground and test box ground. This
cable/resistor probe forms a voltage attenuator between
the resistor and the 50

termination resistance of the test

box. This method allows measurements to be performed

directly on the output pin of the amplifier (pin 6). Since
the CLC44X series has large bandwidths, measurement
equipment should have sufficient bandwidth to accurate-
ly measure pulse and frequency responses of the
CLC44X series.

V. Parts List for Evaluation Boards
Evaluation Board Parts List - Use the device data sheets
with the discussion and examples shown here to select
component values.

I/O connectors (both board styles):

-SMA (straight) Amphenol 901 -144
-SMA (right-angled) Amphenol 901-143

Resistors - 1206 surface-mount type.
Capacitors - Bypassing - 1206 surface-mount type.
Tantalum - TE - Series from Panasonic.

Precision Resistive Products, Inc., Highway 61 South,
Mediapolis, Iowa (319) 394-9131.

http://www.national.com

+Vcc

OUT

C4C3

C6C5

Rin

Rout

-Vcc

730055 REV A
VERY WIDEBAND OP AMP EVAL BOARD

+Vcc

OUT

C4C3

C6C5

Rin

Rout

-Vcc

C o m l i n e a r
WIDE BAND OP AMP R&D TEST BOARD

-Vcc

GND

OUT

+Vcc

COMLINEAR

FORT COLLINS, CO USA

( 970 ) 226 - 0500

-Vcc

OUT

+Vcc

PDIP - Top Side

PDIP - Bottom Side

SOIC - Top Side

SOIC - Bottom Side

http://www.national.com

Lit #660440-002

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Semiconductor Customer Response Group at 1-800-272-9959 or fax 1-800-737-7018.

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president of National Semiconductor Corporation. As used herein:

1. Life support devices or systems are devices or systems which, a) are intended for surgical implant into the body, or b) support or

sustain life, and whose failure to perform, when properly used in accordance with instructions for use provided in the labeling, can
be reasonably expected to result in a significant injury to the user.

2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to

cause the failure of the life support device or system, or to affect its safety or effectiveness.

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circuitry and specifications.

Электронный компонент: CLC730055