AD745AN Analog Devices, AD745AN Datasheet

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AD745AN

Manufacturer Part Number
AD745AN
Description
Ultralow Noise/ High Speed/ BiFET Op Amp
Manufacturer
Analog Devices
Datasheet
a
PRODUCT DESCRIPTION
The AD745 is an ultralow noise, high speed, FET input
operational amplifier. It offers both the ultralow voltage noise
and high speed generally associated with bipolar input op amps
and the very low input currents of FET input devices. Its 20
MHz bandwidth and 12.5 V/ s slew rate makes the AD745 an
ideal amplifier for high speed applications demanding low noise
and high dc precision. Furthermore, the AD745 does not
exhibit an output phase reversal.
REV. C
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
FEATURES
ULTRALOW NOISE PERFORMANCE
2.9 nV/ Hz at 10 kHz
0.38 V p-p, 0.1 Hz to 10 Hz
6.9 fA/ Hz Current Noise at 1 kHz
EXCELLENT AC PERFORMANCE
12.5 V/ s Slew Rate
20 MHz Gain Bandwidth Product
THD = 0.0002% @ 1 kHz
Internally Compensated for Gains of +5 (or –4) or
EXCELLENT DC PERFORMANCE
0.5 mV max Offset Voltage
250 pA max Input Bias Current
2000 V/mV min Open Loop Gain
Available in Tape and Reel in Accordance with
APPLICATIONS
Sonar
Photodiode and IR Detector Amplifiers
Accelerometers
Low Noise Preamplifiers
High Performance Audio
Greater
EIA-481A Standard
1000
100
10
1
100
AD745 & RESISTOR
OP37 & RESISTOR
R
R
SOURCE
SOURCE
OR
1k
E
O
RESISTOR NOISE ONLY
SOURCE RESISTANCE –
10k
(– – –)
RESISTOR
OP37 &
AD745 + RESISTOR
100k
( — )
(
)
1M
10M
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 617/329-4700
The AD745’s guaranteed, tested maximum input voltage noise
of 4 nV/ Hz at 10 kHz is unsurpassed for a FET-input mono-
lithic op amp, as is its maximum 1.0 V p-p noise in a 0.1 Hz to
10 Hz bandwidth. The AD745 also has excellent dc perfor-
mance with 250 pA maximum input bias current and 0.5 mV
maximum offset voltage.
The internal compensation of the AD745 is optimized for
higher gains, providing a much higher bandwidth and a faster
slew rate. This makes the AD745 especially useful as a
preamplifier where low level signals require an amplifier that
provides both high amplification and wide bandwidth at these
higher gains. The AD745 is available in five performance
grades. The AD745J and AD745K are rated over the
commercial temperature range of 0 C to +70 C. The AD745A
and AD745B are rated over the industrial temperature range of
–40 C to +85 C. The AD745S is rated over the military
temperature range of –55 C to +125 C and is available
processed to MIL-STD-883B, Rev. C.
The AD745 is available in 8-pin plastic mini-DIP, 8-pin cerdip,
16-pin SOIC, or in chip form.
8-Pin Plastic Mini-DIP (N) &
8-Pin Cerdip (Q) Packages
OFFSET
120
100
–20
NULL 1
80
60
40
20
0
– IN
–V
+IN
100
S
High Speed, BiFET Op Amp
NC = NO CONNECT
2
3
4
TOP VIEW
AD745
1k
CONNECTION DIAGRAMS
GAIN
10k
FREQUENCY – Hz
8
7
6
5
OUTPUT
NC
+V
OFFSET
NULL
100k
S
OFFSET
Ultralow Noise,
NULL
– IN
–V
+IN
1M
16-Pin SOIC (R) Package
NC
NC
NC
NC
PHASE
S
1
6
8
4
5
2
3
7
10M 100M
TOP VIEW
AD745
AD745
Fax: 617/326-8703
120
100
60
40
20
0
–20
80
16
14
13
11
15
12
10
9
OUTPUT
NC
NC
NC
NC
+V
OFFSET
NULL
NC
S

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AD745AN Summary of contents

Page 1

... SOURCE RESISTANCE – REV. C Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. 8-Pin Plastic Mini-DIP (N) & ...

Page 2

AD745–SPECIFICATIONS Model 1 INPUT OFFSET VOLTAGE Initial Offset Initial Offset vs. Temp. vs. Supply (PSRR) vs. Supply (PSRR) 3 INPUT BIAS CURRENT Either Input Either Input @ T MAX Either Input Either Input INPUT OFFSET ...

Page 3

... V S and – Model AD745JN AD745AN AD745JR- Plastic DIP Small Outline IC C/W METALIZATION PHOTOGRAPH Dimensions shown in inches and (mm). –3– AD745 ORDERING GUIDE Package ...

Page 4

AD745 –Typical Characteristics 10k LOAD – – SUPPLY VOLTAGE VOLTS Figure 1. Input Voltage Swing vs. Supply Voltage ...

Page 5

PHASE GAIN –20 –20 100 1k 10k 100k 1M 10M 100M FREQUENCY – Hz Figure 10. Open-Loop Gain and Phase vs. Frequency 120 110 100 90 ...

Page 6

AD745 –Typical Characteristics 72 TOTAL UNITS = 760 –15 –10 – INPUT OFFSET VOLTAGE DRIFT – Figure 19. Distribution of Offset ...

Page 7

OP AMP PERFORMANCE JFET VS. BIPOLAR The AD745 offers the low input voltage noise of an industry standard bipolar op amp without its inherent input current errors. This is demonstrated in Figure 24, which compares input voltage noise vs. input ...

Page 8

AD745 Figures 26 and 27 show two ways to buffer and amplify the output of a charge output transducer. Both require using an amplifier which has a very high input impedance, such as the AD745. Figure 26 shows a model ...

Page 9

HOW CHIP PACKAGE TYPE AND POWER DISSIPATION AFFECT INPUT BIAS CURRENT As with all JFET input amplifiers, the input bias current of the AD745 is a direct function of device junction temperature, I approximately doubling every 10 C. Figure 30 ...

Page 10

AD745 TWO HIGH PERFORMANCE ACCELEROMETER AMPLIFIERS Two of the most popular charge-out transducers are hydro- phones and accelerometers. Precision accelerometers are typi- cally calibrated for a charge output (pC/g).* Figures 35a and 35b show two ways in which to configure ...

Page 11

Design Considerations for I-to-V Converters There are some simple rules of thumb when designing an I-V converter where there is significant source capacitance (as with a photodiode) and bandwidth needs to be optimized. Consider the circuit of Figure 37. The ...

Page 12

AD745 FOR R >> Figure 40. Optional External Components for Balancing Source Impedances 8-Pin Cerdip ...

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