ADL5306

Rev. 0 | Page 13 of 16

R1

R2

1k

Ω

1k

Ω

1nF

1nF

NC

INPT

VREF

IREF

SCAL

BFIN

VPOS

0.1

µF

COMM

COMM

COMM

COMM

VNEG

VNEG

VSUM

VOUT

VLOG

1

2

3

4

56

78

9

10

11

12

13

14

15

16

ADL5306

03727-0-026

AD8138

EVALUATION

BOARD

HP3577A

NETWORK ANALYZER

+IN

B

A

OUTPUT INPUT R INPUT A INPUT B

POWER

SPLITTER

Figure 26. Configuration for Logarithmic Amplifier Bandwidth Measurement

Figure 26 shows the configuration used for frequency response

measurements of the logarithmic amplifier section. The

AD8138 output is offset to 1.5 V dc and modulated to a depth

of 5% at frequency. R1 is chosen (over a wide range of values up

R1

200k

Ω

1k

Ω

1nF

1k

Ω

1nF

NC

INPT

VREF

IREF

SCAL

BFIN

VPOS

0.1

µF

ALKALINE

"D" CELL

ALKALINE

"D" CELL

COMM

COMM

COMM

COMM

VNEG

VNEG

VSUM

VOUT

VLOG

1

2

3

4

567

8

9

10

11

12

13

14

15

16

ADL5306

03727-0-027

HP89410A

SOURCE TRIGGER CHANNEL 1 CHANNEL 2

Figure 27. Configuration for Noise Spectral Density Measurement

The configuration of Figure 27 is used to measure the noise

performance. Batteries provide both the supply voltage and the

input current in order to minimize the introduction of spurious

noise and ground loop effects. The entire evaluation system,

including the current setting resistors, is mounted in a closed

aluminum enclosure to provide additional shielding to external

noise sources.

R1

200k

Ω

1k

Ω

1nF

1k

Ω

50k

Ω

1nF

NC

INPT

VREF

IREF

SCAL

BFIN

VPOS

0.1

µF

COMM

COMM

COMM

COMM

VNEG

VNEG

VSUM

VOUT

VLOG

1

2

3

4

56

78

9

10

11

12

13

14

15

16

ADL5306

03727-0-028

TDS5104

CH 1

9213

Figure 28. Configuration for Logarithmic Amplifier Pulse Response

Measurement

Figure 28 shows the setup used to make the pulse response

measurements. As with the bandwidth measurement, VLOG is

connected directly to BFIN and the buffer amplifier is

configured for a gain of 1. The buffer’s output is connected

through a short cable to the TDS5104 scope, with the input

impedance set to 1 MΩ. The LeCroy’s output is offset to create

the initial pedestal current for a given R1 value. The pulse then

creates a 1-decade current step.