AD8037AR datasheet(21/23 Pages) AD

21 / 23 page

AD8036/AD8037

REV. A

–21–

Layout Considerations

The specified high speed performance of the AD8036 and

AD8037 requires careful attention to board layout and compo-

nent selection. Proper RF design techniques and low pass para-

sitic component selection are mandatory.

The PCB should have a ground plane covering all unused por-

tions of the component side of the board to provide a low im-

pedance path. The ground plane should be removed from the

area near the input pins to reduce stray capacitance.

Chip capacitors should be used for supply and input clamp by-

passing (see Figure 83). One end should be connected to the

ground plane and the other within 1/8 inch of each power and

clamp pin. An additional large (0.47

µF–10 µF) tantalum elec-

trolytic capacitor should be connected in parallel, though not

necessarily so close, to supply current for fast, large signal

changes at the output.

The feedback resistor should be located close to the inverting

input pin in order to keep the stray capacitance at this node to a

minimum. Capacitance variations of less than 1 pF at the in-

verting input will significantly affect high speed performance.

Stripline design techniques should be used for long signal traces

(greater than about 1 inch). These should be designed with a

characteristic impedance of 50

Ω or 75 Ω and be properly termi-

nated at each end.

Evaluation Board

An evaluation board for both the AD8036 and AD8037 is avail-

able that has been carefully laid out and tested to demonstrate

that the specified high speed performance of the device can be

realized. For ordering information, please refer to the Ordering

Guide.

The layout of the evaluation board can be used as shown or

serve as a guide for a board layout.

VOUT

0.1 F

AD8036/

AD8037

0.1 F

–VS

+VS

–VS

+VS

–VS

+VS

NONINVERTING CONFIGURATION

10 F

+VS

–VS

0.1 F

0.01 F

10 F

0.1 F

0.01 F

OPTIONAL

SUPPLY BYPASSING

Figure 83. Noninverting Configurations for Evaluation

Boards

Table I.

AD8036A

AD8037A

Gain

Component

+10

+100

+10

+100

140

Ω

274

Ω

2 k

Ω

2 k

Ω

274

Ω

2 k

Ω

2 k

Ω

274

Ω

221

Ω

20.5

Ω

274

Ω

221

Ω

20.5

Ω

RO (Nominal)

49.9

Ω

49.9

Ω

49.9

Ω

49.9

Ω

49.9

Ω

49.9

Ω

49.9

Ω

130

Ω

100

Ω

100

Ω

100

Ω

100

Ω

100

Ω

100

Ω

RT (Nominal)

49.9

Ω

49.9

Ω

49.9

Ω

49.9

Ω

49.9

Ω

49.9

Ω

49.9

Ω

Small Signal BW (MHz)

240

1.3

275

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