Datasheet AD640 (Analog Devices)

a
DC-Coupled Demodulating 120 MHz Logarithmic Amplifier AD64 0 FEATURES
signal output at +50 dB (referred to input) is provided to operate
Complete, Fully Calibrated Monolithic System
AD640s in cascade.
Five Stages, Each Having 10 dB Gain, 350 MHz BW
The logarithmic response is absolutely calibrated to within ±1 dB
Direct Coupled Fully Differential Signal Path
for dc or square wave inputs from ± 0.75 mV to ± 200 mV, with
Logarithmic Slope, Intercept and AC Response are
an intercept (logarithmic offset) at 1 mV dc. An integral X10
Stable Over Full Military Temperature Range
attenuator provides an alternative input range of ± 7.5 mV to
Dual Polarity Current Outputs Scaled 1 mA/Decade
±2 V dc. Scaling is also guaranteed for sinusoidal inputs.
Voltage Slope Options (1 V/Decade, 100 mV/dB, etc.)
The AD640B is specified for the industrial temperature range of
Low Power Operation (Typically 220 mW at
ⴞ
5 V)
–40°C to +85°C and the AD640T, available processed to MIL-
Low Cost Plastic Packages Also Available
STD-883B, for the military range of –55°C to +125°C. Both are
APPLICATIONS
available in 20-lead side-brazed ceramic DIPs or leadless chip
Radar, Sonar, Ultrasonic and Audio Systems
carriers (LCC). The AD640J is specified for the commercial
Precision Instrumentation from DC to 120 MHz
temperature range of 0°C to +70°C, and is available in both
Power Measurement with Absolute Calibration
20-lead plastic DIP (N) and PLCC (P) packages.
Wide Range High Accuracy Signal Compression Alternative to Discrete and Hybrid IF Strips
This device is now available to Standard Military Drawing
Replaces Several Discrete Log Amp ICs
(DESC) number 5962-9095501MRA and 5962-9095501M2A.
PRODUCT HIGHLIGHTS PRODUCT DESCRIPTION
1. Absolute calibration of a wideband logarithmic amplifier is The AD640 is a complete monolithic logarithmic amplifier. A single unique. The AD640 is a high accuracy measurement device, AD640 provides up to 50 dB of dynamic range for frequencies not simply a logarithmic building block. from dc to 120 MHz. Two AD640s in cascade can provide up to 95 dB of dynamic range at reduced bandwidth. The AD640 uses a 2. Advanced design results in unprecedented stability over the successive detection scheme to provide an output current propor- full military temperature range. tional to the logarithm of the input voltage. It is laser calibrated to 3. The fully differential signal path greatly reduces the risk of close tolerances and maintains high accuracy over the full military instability due to inadequate power supply decoupling and temperature range using supply voltages from ±4.5 V to ± 7.5 V. shared ground connections, a serious problem with com- monly used unbalanced designs. The AD640 comprises five cascaded dc-coupled amplifier/limiter stages, each having a small signal voltage gain of 10 dB and a –3 dB 4. Differential interfaces also ensure that the appropriate ground bandwidth of 350 MHz. Each stage has an associated full-wave connection can be chosen for each signal port. They further detector, whose output current depends on the absolute value of its increase versatility and simplify applications. The signal input input voltage. The five outputs are summed to provide the video impedance is ~500 kΩ in shunt with ~2 pF. output (when low-pass filtered) scaled at 1 mA per decade (50 µA 5. The dc-coupled signal path eliminates the need for numerous per dB). On chip resistors can be used to convert this output cur- interstage coupling capacitors and simplifies logarithmic rent to a voltage with several convenient slope options. A balanced conversion of subsonic signals. (continued on page 4)
FUNCTIONAL BLOCK DIAGRAM RG1 RG0 1k
V
1k
V
RG2 LOG OUT LOG COM 17 16 15 14 INTERCEPT POSITIONING BIAS 12 +V 13 S COM 18 ATN OUT 19 FULL-WAVE FULL-WAVE FULL-WAVE FULL-WAVE FULL-WAVE DETECTOR DETECTOR DETECTOR DETECTOR DETECTOR SIG +IN 20 11 SIG +OUT 10dB 10dB 10dB 10dB 10dB SIG –IN 1 10 SIG –OUT AMPLIFIER/LIMITER ATN LO 2 AMPLIFIER/LIMITER AMPLIFIER/LIMITER AMPLIFIER/LIMITER AMPLIFIER/LIMITER 27
V
ATN COM 3 9 BL2 30
V
270
V
ATN COM 4 5 6 GAIN BIAS REGULATOR 7 SLOPE BIAS REGULATOR 8 ITC ATN IN BL1 –VS
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Document Outline AD640-SPECIFICATIONS DC Specifications AC Specifications Thermal Characteristics ABSOLUTE MAXIMUM RATINGS TYPICAL DC PERFORMANCE CHARACTERISTICS TYPICAL AC PERFORMANCE CHARACTERISTICS OUTLINE DIMENSIONS ORDERING GUIDE