AD8306 Analog Devices Data Sheet Manual

5 MHz–400 MHz 100 d B High Precision Limiting-Logarithmic Amplifier

AD8306

FUNCTIONAL BLOCK DIAGRAMFEATURES

Complete, Fully Calibrated Log-Limiting IF Amplifier 100 d B Dynamic Range: –91 d BV to +9 d BV

SIX STAGES TOTAL GAIN 72d B TYP GAIN 18d B

Stable RSSI Scaling Over Temperature and Supplies:

INHI LMHI

20 m V/d B Slope, –95 d Bm Intercept 12d B 12d B 12d B LIM

INLO LMLO

60.4 d B RSSI Linearity up to 200 MHz

Programmable Limiter Gain and Output Current LADR ATTEN BIAS

DET DET4 3 DET DET

Differential Outputs to 10 m A, 2.4 V p-p Overall Gain 90 d B, Bandwidth 400 MHz I–V VLOG Constant Phase (Typical 656 ps Delay Skew) TEN DETECTORS SPACED 12d B

Single Supply of +2.7 V to +6.5 V at 16 m A Typical Fully Differential Inputs, RIN = 1 k V, CIN = 2.5 p F GAIN BAND-GAP SLOPE INTERCEPT

BIAS REFERENCEENBL BIAS TEMP COMP

500 ns Power-Up Time, <1 m A Sleep Current

APPLICATIONS Receivers for Frequency and Phase Modulation Very Wide Range IF and RF Power Measurement Receiver Signal Strength Indication (RSSI) Low Cost Radar and Sonar Signal Processing Instrumentation: Network and Spectrum Analyzers

PRODUCT DESCRIPTION The overall dynamic range for this combination extends from The AD8306 is a complete IF limiting amplifier, providing both –91 d BV (–78 d Bm at the 50 Ω level) to a maximum permissible an accurate logarithmic (decibel) measure of the input signal value of +9 d BV, using a balanced drive of antiphase inputs each of (the RSSI function) over a dynamic range of 100 d B, and a 2 V in amplitude, which would correspond to a sine wave power

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programmable limiter output, useful from 5 MHz to 400 MHz. of +22 d Bm if the differential input were terminated in 50 Ω. Through laser trimming, the slope of the RSSI output is closely

It is easy to use, requiring few external components. A single

controlled to 20 m V/d B, while the intercept is set to –108 d BV

supply voltage of +2.7 V to +6.5 V at 16 m A is needed, corre-

(–95 d Bm re 50 Ω). These scaling parameters are determined

sponding to a power consumption of under 50 m W at 3 V, plus

by a band-gap voltage reference and are substantially indepen-

the limiter bias current, determined by the application and typi-

dent of temperature and supply. The logarithmic law conform-

cally 2 m A, providing a limiter gain of 90 d B when using 200

ance is typically within ±0.4 d B over the central 80 d B of this

loads. A CMOS-compatible control interface can enable the

range at any frequency between 10 MHz and 200 MHz, and is

AD8306 within about 500 ns and disable it to a standby current

degraded only slightly at 400 MHz.

of under 1 µA.

The RSSI response time is nominally 73 ns (10%–90%). The

The six cascaded amplifier/limiter cells in the main path have a

averaging time may be increased without limit by the addition of

small signal gain of 12.04 d B (×4), with a –3 d B bandwidth of

an external capacitor. The full output of 2.34 V at the maximum

850 MHz, providing a total gain of 72 d B. The programmable

input of +9 d BV can drive any resistive load down to 50 Ω and

output stage provides a further 18 d B of gain. The input is fully

this interface remains stable with any value of capacitance on

differential and presents a moderately high impedance (1 kΩ in

the output.

parallel with 2.5 p F). The input-referred noise-spectral-density,

when driven from a terminated 50 Ω, source is 1.28 n V/√Hz, The AD8306 is fabricated on an advanced complementary equivalent to a noise figure of 3 d B. The sensitivity of the bipolar process using silicon-on-insulator isolation techniques AD8306 can be raised by using an input matching network. and is available in the industrial temperature range of –40°C to +85°C, in a 16-lead narrow body SO package. The AD8306 is

Each of the main gain cells includes a full-wave detector. An

also available for the full military temperature range of –55°C to

additional four detectors, driven by a broadband attenuator, are

+125°C, in a 16-lead side-brazed ceramic DIP.

used to extend the top end of the dynamic range by over 48 d B.

REV. A Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its

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which may result from its use. No license is granted by implication or Tel: 781/329-4700 World Wide Web Site: http://www.analog.com otherwise under any patent or patent rights of Analog Devices. Fax: 781/326-8703 © Analog Devices, Inc., 1999