AD8313

Rev. D | Page 22 of 24

R2

10

Ω

EXT ENABLE

SW1

R1

10

Ω

1

2

3

4

INHI

INLO

VPOS PWDN

COMM

VSET

AD8313

8

7

6

5

INHI

VOUT

EXT VSET

AD8009

VPOS

VOUT

C7

0.1

µF

C1

680pF

C2

680pF

C3

0.1

µF

C5

0.1

µF

R4

0

Ω

R12

301

Ω

R5

0

Ω

R7

0

Ω

R3

0

Ω

R11

0

Ω

R9

0

Ω

R2

10

Ω

L/R

53.6

Ω

INLO

TP1

Z1

Z2

R10

OPEN

R6

OPEN

R8

20k

Ω

C6

OPEN

A

B

C4

0.1

µF

Figure 44. Evaluation Board Schematic

Table 7. Evaluation Board Configuration Options

Component

Function

Default

VPS1, VPS2,

GND, VNEG

Supply Pins. VPS1 is the positive supply pin for the AD8313. VPS2 and VNEG are the

positive and negative supply pins for the AD8009. If the AD8009 is being operated

from a single supply, VNEG should be connected to GND. VPS1 and VPS2 are

independent. GND is shared by both devices.

Not Applicable

Z1

AD8313 Logarithmic Amplifier. If the AD8313 is used in measurement mode, it is not

necessary to power up the AD8009 op amp. The log output can be measured at TP1 or

at the SMA connector labeled VSET.

Installed

Z1

AD8009 Operational Amplifier.

Installed

SW1

Device Enable. When in Position A, the PWDN pin is connected to ground and the

AD8313 is in normal operating mode. In Position B, the PWDN pin is connected to an

SMA connector labeled ENBL. A signal can be applied to this connector.

SW1 = A

R7, R8

Slope Adjust. The slope of the AD8313 can be increased from its nominal value of

18 mV/dB to a maximum of 40 mV/dB by removing R11, the 0 Ω resistor, which shorts

VSET to VOUT, and installing a 0 Ω resistor at R7. The 20 kΩ potentiometer at R8 can

then be used to change the slope.

R7 = 0 Ω (Size 0603)

R8 = installed

Operating in Controller Mode. To put the AD8313 into controller mode, R7 and R11

should be removed, breaking the link between VOUT and VSET. The VSET pin can then

be driven externally via the SMA connector labeled VSET.

L/R, C1, C2, R9

Input Interface. The 52.3 Ω resistor in position L/R, along with C1 and C2, create a

wideband 50 Ω input. Alternatively, the 52.3 Ω resistor can be replaced by an inductor

to form an input matching network. See Input Coupling section for more details.

Remove the 0 Ω resistor at R9 for differential drive applications.

L/R = 53.6 Ω (Size 0603)

C1 = C2 = 680 pF (Size 0603)

R9 = 0 Ω (Size 0603)

R10, R12

Op Amp Gain Adjust. The AD8009 is initially configured as a buffer; gain = 1. To increase

the gain of the op amp, modify the resistor values R10 and R12.

R10 = open (Size 0603)

R12 = 301 Ω (Size 0603)

R5, R6, C6

Op Amp Output Loading/Filtering. A variety of loading and filtering options are

available for the AD8009. The robust output of the op amp is capable of driving low

impedances such as 50 Ω or 75 Ω, configure R5 and R6 accordingly. See the AD8009

data sheet for more details.

R5 = 0 Ω (Size 0603)

R6 = open (Size 0603)

C6 = open (Size 0603)

R1, R2, R3, R4,

C3, C4, C5, C7

Supply Decoupling.

R1 = R2 = 10 Ω (Size 0603)

R3 = R4 = 0 Ω (Size 0603)

C3 = C4 = 0.1 µF (Size 0603)

C5 = C7 = 0.1 µF (Size 0603)