Low Cost, DC to 500 MHz, 92 dB

Logarithmic Amplifier

Data Sheet

AD8307

Rev. F

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FEATURES

Complete multistage logarithmic amplifier

92 dB dynamic range: −75 dBm to +17 dBm to −90 dBm

using matching network

Single supply of 2.7 V minimum at 7.5 mA typical

DC to 500 MHz operation, ±1 dB linearity

Slope of 25 mV/dB, intercept of −84 dBm

Highly stable scaling over temperature

Fully differential dc-coupled signal path

100 ns power-up time, 150 μA sleep current

APPLICATIONS

Conversion of signal level to decibel form

Transmitter antenna power measurement

Receiver signal strength indication (RSSI)

Low cost radar and sonar signal processing

Network and spectrum analyzers (to 120 dB)

Signal level determination down to 20 Hz

True decibel ac mode for multimeters

FUNCTIONAL BLOCK DIAGRAM

BAND GAP REFERENCE

AND BIASING

SIX 14.3dB 900MHz

AMPLIFIER STAGES

MIRROR

INPUT-OFFSET

COMPENSATION LOOP

COM

INM

INP

ENB

VPS

INT

OUT

OFS

AD8307

7.5mA

1.1kΩ

3

2

2µA

/dB

12.5kΩ

COM

NINE DETECTOR CELLS

SPACED 14.3dB

–INP

+INP

8

1

2

7

5

6

4

3

Figure 1.

GENERAL DESCRIPTION

The AD8307 is the first logarithmic amplifier made available in

an 8-lead SOIC_N package. It is a complete 500 MHz monolithic

demodulating logarithmic amplifier based on the progressive

compression (successive detection) technique, providing a

dynamic range of 92 dB to ±3 dB law conformance and 88 dB

to a tight ±1 dB error bound at all frequencies up to 100 MHz.

The AD8307 is extremely stable and easy to use, requiring no

significant external components. A single-supply voltage of

2.7 V to 5.5 V at 7.5 mA is needed. A fast acting CMOS-

compatible control pin can disable the AD8307 to a standby

current of 150 μA.

The AD8307 operates over the industrial temperature range of

−40°C to +85°C and is available in an 8-lead SOIC package and

an 8-lead PDIP.

Table 1. Next Generation Upgrades for the AD8307

Device No.

Product Description

AD8310

15 ns Response Time, Buffered Output

ADL5513

Lower Input Range (80 dB), Operation to 4 GHz,

Higher Power Consumption

AD8309

Higher Input Range (100 dB), Limiter Output