CLC730036 datasheet(2/6 Pages) NSC

2 / 6 page

Layout Considerations

General layout and supply bypassing play major roles in

high frequency performance. When designing your own

board, use the evaluation board as a guide and follow

these steps as a basis for high frequency layout:

1. Use a ground plane.

2. Include 6.8

µF tantalum and 0.1µF ceramic

capacitors on both supplies.

3. Place the 6.8

µF capacitors within 0.75 inches

of the power pins.

4. Place the 0.1

µF capacitors less than 0.1

inches from the power pins.

5. Remove the ground plane under and around

the part, especially near the input and output

pins to reduce parasitic capacitance.

6. Minimize all trace lengths to reduce series

inductances.

7. Use individual flush-mount sockets, for prototyping.

Measurement Hints

If 50

Ω coax and 50Ω R

in/Rout resistors are used, many of

the typical performance plots found in the product data

sheets can be reproduced.

When SMA connectors and cables are not available to

evaluate the amplifier, do not use normal oscilloscope

probes. Use low impedance resistive divider probes of

100 to 500

Ω. If a low impedance probe is not available,

then a section of 50

Ω coaxial cable and a low impedance

resistor (10

Ω to 50Ω) may be used. Follow these 3 steps

to create a “cable/resistor” probe:

1. Connect one end of the coax’s center to a test

measurement box terminated in 50

Ω.

2. Connect the other end of the cable’s center

conductor to the low impedance resistor. (The

open side of the resistor is now a probe.)

3. Connect the ground shield of the cable to

evaluation board ground and test box ground.

Figure 4: “Cable/Resistor” Probe Configuration

This “cable/resistor” probe, shown in Figure 4, forms a

voltage attenuator between the resistor and the 50

Ω

termination resistance of the test box.

This method

allows measurements to be performed directly on the

output pin of the amplifier.

When evaluating only one channel on the board,

complete the following on the unused channel:

1. Included Rf and Rg as shown in Figure 1

2. Ground the input

3. Load the output with 50

Ω to ground

Power Supplies

Refer to the product data sheet for the recommended

supply voltages.

Component Values

Rf, Rg - Use the product data sheet to

select values

Rin, Rout - 50Ω (Refer to Basic Operation

section for details)

Rt - Optional resistor for inverting gain

configurations (Refer

Inverting Gain

Operation section for details)

C3, C4 - 6.8

µF tantalum capacitors

C1, C2 - 0.1

µF ceramic capacitors

http://www.national.com

Test Box and

Evaluation Board

Ground

Ω Coaxial

Cable

Low Impedance

Resistor

Probe

Test Box

(terminated

in 50

Ω)

CLC730036 Datasheet(PDF) 2 Page - National Semiconductor (TI)

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