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AD8331/AD8332/AD8334

Rev. G | Page 43 of 56

AD8332 EVALUATION BOARD

GENERAL DESCRIPTION

The AD8332-EVALZ is a platform for the testing and evaluation of

the AD8332 variable gain amplifier (VGA). The board is shipped

assembled and tested, and users need only connect the signal

and VGAIN sources to a single 5 V power supply. Figure 104 is a

photograph of the component side of the board, and Figure 105

shows the schematic. The AD8332-EVALZ is lead free and

RoHS compliant.

Figure 104.Photograph of the AD8332-EVALZ

USER-SUPPLIED OPTIONAL COMPONENTS

The board is built and tested using the components shown in

black in Figure 105. Provisions are made for optional components

(shown in gray) that can be installed for testing at user discretion.

The default LNA input impedance is 50 Ω to match various

signal generators and network analyzers. Input impedances up to

6 kΩ are realized by changing the values of RFBx and CSHx. For

reference, Table 11 lists the common input impedance values

and corresponding adjustments. The board is designed for 0603

size, surface-mount components.

Table 11. LNA External Component Values for Common

Source Impedances

RIN (Ω)

RFB1, RFB2 (Ω Std 1% Value)

CSH1, CSH2 (pF)

274

412

100

562

200

1.13 k

1.2

500

3.01 k

None

6 k

∞

None

SMA connectors, S2, S3, S6, and S7, are provided for access to

the LNA outputs or the VGA inputs. If the LNA is used alone,

0.1 μF coupling capacitors can be installed at the C5, C9, C23,

and C24 locations. Resistors of 68 Ω to 100 Ω may be required

if the load capacitances, as seen by the LNA outputs, are larger

than approximately 10 pF.

A resistor can be inserted at RCLMP if output clamping is desired.

The peak-to-peak clamping level is adjusted by installing one of

the standard 1% resistor values listed in Table 8.

A high frequency differential probe connected to the 2-pin headers,

VOx, is the preferred method to observe a waveform at the VGA

output. A typical setup is shown in Figure 106. Single-ended loads

can be connected directly via the board edge SMA connectors.

Note that the AD8332 output amplifier is buffered with 237 Ω

resistors; therefore, be sure to compensate for attenuation if low

impedances are connected to the output SMAs.

MEASUREMENT SETUP

The basic board connections for measuring bandwidth are

shown in Figure 106. A 5 V, 100 mA (minimum) power supply

is required, and a low noise voltage reference supply is required

for VGAIN.

BOARD LAYOUT

The evaluation board circuitry uses four conductor layers.

The two inner layers are power and ground planes, and all

interconnecting circuitry is located on the outer layers. Figure 108

to Figure 111 illustrate the copper patterns.

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