Analog Devices AD645SH-883B, AD645KN, AD645JN, AD645CH, AD645BH Datasheet

a	Low Noise, Low Drift
	FET Op Amp

FEATURES

Improved Replacement for Burr-Brown

OPA-111 and OPA-121 Op Amp

LOW NOISE

2 mV p-p max, 0.1 Hz to 10 Hz 10 nV/ÖHz max at 10 kHz

11 fA p-p Current Noise 0.1 Hz to 10 Hz

HIGH DC ACCURACY

250 mV max Offset Voltage

1 mV/8C max Drift

IMPROVEDDRIFT

1.5 pA max Input Bias Current

114 dB Open-Loop Gain

Available in Plastic Mini-DIP, 8-Pin Header Packages, or Chip Form

APPLICATIONS

Low Noise Photodiode Preamps

CT Scanners

Precision I-V Converters

PRODUCT DESCRIPTION

The AD645 is a low noise, precision FET input op amp. It offers the pico amp level input currents of a FET input device coupled with offset drift and input voltage noise comparable to a high performance bipolar input amplifier.

The AD645 has been improved to offer the lowest offset drift in a FET op amp, 1 mV/°C. Offset voltage drift is measured and trimmed at wafer level for the lowest cost possible. An inherently low noise architecture and advanced manufacturing techniques result in a device with a guaranteed low input voltage noise of 2 mV p-p, 0.1 Hz to 10 Hz. This level of dc performance along with low input currents make the AD645 an excellent choice for high impedance applications where stability is of prime concern.

DENSITY	1k
SPECTRALNOISE nV/Hz	10
	100
VOLTAGE
	1.0
	1		10	100	1k	10k
				FREQUENCY – Hz

Figure 1. AD645 Voltage Noise Spectral Density vs. Frequency

REV. B

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.

	AD645
CONNECTION DIAGRAMS
8-Pin Plastic Mini-DIP	TO-99 (H) Package
(N) Package

CASE

OFFSET	1		8	NC	OFFSET		8	+V
NULL					NULL	1
		AD645						7
–IN	2		7	+VS
					– IN	2		6	OUTPUT
+IN	3		6	OUTPUT
						3	AD645	5
–VS	4	TOP VIEW	5	OFFSET	+ IN		4	OFFSET
				NULL				NULL
	NC = NO CONNECT						– V
					NOTE: CASE IS CONNECTED
					TO PIN 8

The AD645 is available in six performance grades. The AD645J and AD645K are rated over the commercial temperature range of 0°C to +70°C. The AD645A, AD645B, and the ultraprecision AD645C are rated over the industrial temperature range of –40°C to +85°C. The AD645S is rated over the military temperature range of –55°C to +125°C and is available processed to MIL-STD-883B.

The AD645 is available in an 8-pin plastic mini-DIP, 8-pin header, or in die form.

PRODUCT HIGHLIGHTS

1.Guaranteed and tested low frequency noise of 2 mV p-p max and 20 nV/ÖHz at 100 Hz makes the AD645C ideal for low noise applications where a FET input op amp is needed.

2.Low VOS drift of 1 mV/°C max makes the AD645C an excellent choice for applications requiring ultimate stability.

3.Low input bias current and current noise (11 fA p-p 0.1 Hz to 10 Hz) allow the AD645 to be used as a high precision preamp for current output sensors such as photodiodes, or as a buffer for high source impedance voltage output sensors.

	30
	25
OF UNITS	20
	15
NUMBER
	10
	5
	0
	–2.5	–2.0	–1.5	–1.0	–0.5	0.0	0.5	1.0	1.5	2.0	2.5
			INPUT OFFSET VOLTAGE DRIFT– V/°C

Figure 2. Typical Distribution of Average Input Offset Voltage Drift (196 Units)

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: [phone] Fax: [phone]

AD645–SPECIFICATIONS(@ +258C, and 615 V dc, unless otherwise noted)

Model			AD645J/A			AD645K/B			AD645C			AD645S
	Conditions1	Min	Typ	Max	Min	Typ	Max	Min	Typ	Max	Min	Typ	Max	Units
INPUT OFFSET VOLTAGE1
Initial Offset			100	500		50	250		50	250		100	500	mV
Offset	TMIN –TMAX		300	1000		100	400		75	300		500	1500	mV
Drift (Average)			3	10/5		1	5/2		0.5	1		4	10	mV/°C
vs. Supply (PSRR)		90	110		94	110		94	110		90	110		dB
vs. Supply	TMIN –TMAX		100		90	100		90	100		86	95		dB
INPUT BIAS CURRENT2
Either Input	VCM = 0 V		0.7/1.8	3/5		0.7/1.8 1.5/3			1.8	3		1.8	5	pA
Either Input
@ TMAX	VCM = 0 V		16/115			16/115			115			1800		pA
Either Input	VCM = +10 V		0.8/1.9			0.8/1.9			1.9			1.9		pA
Offset Current	VCM = 0 V		0.1	1.0		0.1	0.5		0.1	0.5		0.1	1.0	pA
Offset Current
@ TMAX	VCM = 0 V		2/6			2/6			6			100		pA
INPUT VOLTAGE NOISE	0.1 to 10 Hz		1.0	3.0		1.0	2.5		1	2		1.0	3.3	mV p-p
	f = 10 Hz		20	50		20	40		20	40		20	50	nV/Ö		Hz
	f = 100 Hz		10	30		10	20		10	20		10	30	nV/Ö
																Hz
	f = 1 kHz		9	15		9	12		9	12		9	15	nV/Ö		Hz
	f = 10 kHz		8	10		8	10		8	10		8	10	nV/Ö
																Hz
INPUT CURRENT NOISE	f = 0.1 to 10 Hz		11	20		11	15		11	15		11	20	fA p-p
	f = 0.1 thru 20 kHz		0.6	1.1		0.6	0.8		0.6	0.8		0.6	1.1	fA/Ö
															Hz
FREQUENCY RESPONSE
Unity Gain, Small Signal			2			2			2			2		MHz
Full Power Response	VO = 20 V p-p
	RLOAD = 2 kW	16	32		16	32		16	32		16	32		kHz
Slew Rate, Unity Gain	VOUT = 20 V p-p
	RLOAD = 2 kW	1	2		1	2		1	2		1	2		V/ms
SETTLING TIME3
To 0.1%			6			6			6			6		ms
To 0.01%			8			8			8			8		ms
Overload Recovery4	50% Overdrive		5			5			5			5		ms
Total Harmonic	f = 1 kHz
Distortion	RLOAD ³ 2 kW
	VO = 3 V rms		0.0006			0.0006			0.0006			0.0006		%
INPUT IMPEDANCE
Differential	VDIFF = ± 1 V		1012i1			1012i1			1012i1			1012i1		WipF
Common-Mode			1014i2.2			1014i2.2			1014i2.2			1014i2.2		WipF
INPUT VOLTAGE RANGE
Differential5		± 10	± 20		± 10	± 20		± 10	± 20		± 10	± 20		V
Common-Mode Voltage			+11, –10.4			+11, –10.4			+11, –10.4			+11, –10.4		V
Over Max Oper. Range		± 10			± 10			± 10			± 10			V
Common-Mode
Rejection Ratio	VCM = ±10 V	90	110		94	110		94	110		90	110		dB
	TMIN–TMAX		100		90	100		90	100		86	100		dB
OPEN-LOOP GAIN	VO = ±10 V
	RLOAD ³ 2 kW	114	130		120	130		120	130		114	130		dB
	TMIN –TMAX				114			114			110			dB
OUTPUT CHARACTERISTICS
Voltage	RLOAD ³ 2 kW	± 10	± 11		± 10	± 11		± 10	± 11		± 10	± 11		V
	TMIN –TMAX	± 10			± 10			± 10			± 10			V
Current	VOUT = ± 10 V	± 5	± 10		± 5	± 10		± 5	± 10		± 5	± 10		mA
	Short Circuit		± 15			± 15			± 15			± 15		mA
POWER SUPPLY
Rated Performance		± 5	± 15	± 18	± 5	± 15	± 18	± 5	± 15	± 18	± 5	± 15	± 18	V
Operating Range														V
Quiescent Current			3.0	3.5		3.0	3.5		3.0	3.5		3.0	3.5	mA
Transistor Count	# of Transistors		62			62			62			62

NOTES

1Input offset voltage specifications are guaranteed after 5 minutes of operation at T A = +25°C.

2Bias current specifications are guaranteed maximum at either input after 5 minutes of operation at TA = +25°C. For higher temperature, the current doubles every 10°C. 3Gain = –1, RLOAD = 2 kW.

4Defined as the time required for the amplifier’s output to return to normal operation after removal of a 50% overload from the amplifier input. 5Defined as the maximum continuous voltage between the inputs such that neither input exceeds ± 10 V from ground.

All min and max specifications are guaranteed. Specifications subject to change without notice.

–2–

REV. B

AD645

ABSOLUTE MAXIMUM RATINGS1

Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±18 V Internal Power Dissipation2 (@ TA = +25°C)

8-Pin Header Package . . . . . . . . . . . . . . . . . . . . . . 500 mW 8-Pin Mini-DIP Package . . . . . . . . . . . . . . . . . . . . 750 mW

Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±VS Output Short Circuit Duration . . . . . . . . . . . . . . . . Indefinite

Differential Input Voltage . . . . . . . . . . . . . . . . . . +VS and –VS Storage Temperature Range (H) . . . . . . . . . –65°C to +150°C Storage Temperature Range (N) . . . . . . . . . –65°C to +125°C Operating Temperature Range

AD645J/K . . . . . . . . . . . . . . . . . . . . . . . . . . . 0°C to +70°C

CAUTION

AD645A/B/C . . . . . . . . . . . . . . . . . . . . . . . –40°C to +85°C AD645S . . . . . . . . . . . . . . . . . . . . . . . . . . –55°C to +125°C

Lead Temperature Range

(Soldering 60 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . . +300°C

NOTES

1Stresses above those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

2Thermal Characteristics:

8-Pin Plastic Mini-DIP Package: θJA = 100°C/Watt 8-Pin Header Package: θJA = 200°C/Watt

ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although the AD645 features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.

WARNING!

ESD SENSITIVE DEVICE

ORDERING GUIDE

Model1	Temperature Range	Package Option2
AD645JN	0°C to +70°C	N-8
AD645KN	0°C to +70°C	N-8
AD645AH	–40°C to +85°C	H-08A
AD645BH	–40°C to +85°C	H-08A
AD645CH	–40°C to +85°C	H-08A
AD645SH/883B	–55°C to +125°C	H-08A

NOTES

1Chips are also available.

2N = Plastic Mini-DIP; H = Metal Can.

+VS

2 7

AD645 6

5

3 1

4 10k

VOS ADJUST

–VS

METALIZATION PHOTOGRAPH

Dimensions shown in inches and (mm).

Contact factory for latest dimensions.

NUMBER OF UNITS

Figure 3. AD645 Offset Null Configuration

800
700
600
500
400
300
200
100
0
–1.0	–0.8	–0.6	–0.4	–0.2	0.0	0.2	0.4	0.6	0.8	1.0

INPUT OFFSET VOLTAGE – mV

	120
	110
	100
UNITS	90								UNITS
	80
OF	70								OF
	60
NUMBER									NUMBER
	30
	50
	40
	20
	10
	0	0.5	1.0	1.5	2.0	2.5	3.0	3.5	4.0
	0.0

INPUT BIAS CURRENT – pA

25

20

15

10

5

0

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

INPUT VOLTAGE NOISE – V p-p

	Figure 4. Typical Distribution of Input	Figure 5. Typical Distribution of Input	Figure 6. Typical Distribution of 0.1 Hz
	Offset Voltage (1855 Units)	Bias Current (576 Units)
			to 10 Hz Voltage Noise (202 Units)

REV. B

–3–