Datasheet AD8508 Datasheet (ANALOG DEVICES)

20 μA Maximum, Rail-to-Rail I/O,

www.BDTIC.com/ADI

Zero Input, Crossover Distortion Amplifiers

Preliminary Technical Data

FEATURES

PSRR: 100 dB minimum
CMRR: 105 dB typical
Very low supply current: 20 μA per amp maximum

1.8 V to 5 V single-supply or ±0.9 V to ±2.5 V dual-supply
operation

Rail-to-rail input and output

2.5 mV offset voltage maximum

Very low input bias current: 1 pA typical

APPLICATIONS

Pressure and position sensors
Remote security
Bio sensors
IR thermometers
Battery-powered consumer equipment
Hazard detectors

GENERAL DESCRIPTION

The AD8508 is a quad micropower amplifiers featuring rail-to­rail input and output swings while operating from a 1.8 V to 5 V
single or from ±0.9 V to ±2.5 V dual power supply.

Using a novel circuit technology, these low cost amplifiers offer
zero crossover distortion (excellent PSRR and CMRR perform­ance) and very low bias current, while operating with a supply
current of less than 20 μA per amplifier. This amplifier offers
the lowest noise in its power class.

This combination of features makes the AD8508 amplifiers
ideal choices for battery-powered applications because they
minimize errors due to power supply voltage variations over the
lifetime of the battery and maintain high CMRR even for a rail­to-rail input op amp.

AD8508

PIN CONFIGURATION

1

OUT A

2

–IN A

3

+IN A

+IN B
–IN B

OUT B

Figure 1. 14-Lead TSSOP (RU-14)

V+

AD8508

TOP VIEW

4

(Not to Scale)

5
6
7

Remote battery-powered sensors, handheld instrumentation
and consumer equipment, hazard detection (for example, smoke,
fire, and gas), and patient monitors can benefit from the features
of the AD8508 amplifiers.

The AD8508 are specified for both the industrial temperature
range of −40°C to +85°C and the extended industrial temperature
range of −40°C to +125°C. The AD8508 quad amplifiers are
available in the 14-lead TSSOP package.

14
13
12
11
10

9
8

OUT D
–IN D
+IN D
V–
+IN C
–IN C
OUT C

06900-045

Rev. PrA

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responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
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Tel: [phone] www.analog.com
Fax: [phone] ©2008 Analog Devices, Inc. All rights reserved.

AD8508 Preliminary Technical Data

www.BDTIC.com/ADI

SPECIFICATIONS

ELECTRICAL CHARACTERISTICS—5 V OPERATION

VSY = 5 V, VCM = VSY/2, TA = 25°C, RL = 100 kΩ to GND, unless otherwise noted.

Table 1.

Parameter Symbol Conditions Min Typ Max Unit

INPUT CHARACTERISTICS

Offset Voltage VOS 0 V ≤ VCM ≤ 5 V 0.5 2.5 mV

−40°C ≤ TA ≤ +125°C 3.5 mV
Input Bias Current IB 1 10 pA

−40°C ≤ TA ≤ +85°C 100 pA

−40°C ≤ TA ≤ +125°C 600 pA
Input Offset Current IOS 0.5 5 pA

−40°C ≤ TA ≤ +85°C 50 pA

−40°C ≤ TA ≤ +125°C 130 pA
Input Voltage Range −40°C ≤ TA ≤ +125°C 0 5 V
Common-Mode Rejection Ratio CMRR 0 V ≤ VCM ≤ 5 V 90 105 dB

−40°C ≤ TA ≤ +85°C 90 dB

−40°C ≤ TA ≤ +125°C 85 dB
Large Signal Voltage Gain AVO 0.05 V ≤ V

−40°C ≤ TA ≤ +125°C 100 dB
Offset Voltage Drift

Input Capacitance Differential Mode
Input Capacitance Common Mode

OUTPUT CHARACTERISTICS

Output Voltage High VOH R

−40°C ≤ TA ≤ +125°C 4.98 V
R

−40°C ≤ TA ≤ +125°C 4.9 V
Output Voltage Low VOL R

−40°C ≤ TA ≤ +125°C 5 mV
R

−40°C ≤ TA ≤ +125°C 30 mV
Short-Circuit Limit ISC ±55 mA

POWER SUPPLY

Power Supply Rejection Ratio PSRR VSY = 1.8 V to 5 V 100 110 dB

−40°C ≤ TA ≤ +85°C 100 dB

−40°C ≤ TA ≤ +125°C 95 dB
Supply Current per Amplifier ISY V

−40°C ≤ TA ≤ +125°C 25 μA

DYNAMIC PERFORMANCE

Slew Rate SR RL = 100 kΩ, CL = 10 pF, G = 1 13 mV/μs
Gain Bandwidth Product GBP RL = 1 MΩ, CL = 20 pF, G = 1 95 kHz
Phase Margin ΦM R

NOISE PERFORMANCE

Voltage Noise en p-p f = 0.1 Hz to 10 Hz 2.8 μV p-p
Voltage Noise Density en f = 1 kHz 45 nV/√Hz
Current Noise Density in f = 1 kHz 15 fA/√Hz

ΔV
C

DIFF

CCM

OS

/ΔT

−40°C ≤ T
3 pF

4.2 pF

= 100 kΩ to GND 4.98 4.99 V

L

= 10 kΩ to GND 4.9 4.95 V

L

= 100 kΩ to VSY 2 5 mV

L

= 10 kΩ to VSY 10 25 mV

L

= VSY/2 15 20 μA

OUT

= 1 MΩ, CL = 20 pF, G = 1 60 Degrees

L

≤ 4.95 V 105 120 dB

OUT

≤ +125°C 2 μV/°C

A

Rev. PrA | Page 2 of 4

Preliminary Technical Data AD8508

www.BDTIC.com/ADI

ELECTRICAL CHARACTERISTICS—1.8 V OPERATION

VSY = 1.8 V, VCM = VSY/2, TA = 25°C, RL = 100 kΩ to GND, unless otherwise noted.

Table 2.

Parameter Symbol Conditions Min Typ Max Unit

INPUT CHARACTERISTICS

Offset Voltage VOS 0 V ≤ VCM ≤ 1.8 V 0.5 2.5 mV

−40°C ≤ TA ≤ +125°C 3.5 mV
Input Bias Current IB 1 10 pA

−40°C ≤ TA ≤ +85°C 100 pA

−40°C ≤ TA ≤ +125°C 600 pA
Input Offset Current IOS 0.5 5 pA

−40°C ≤ TA ≤ +85°C 50 pA

−40°C ≤ TA ≤ +125°C 100 pA
Input Voltage Range −40°C ≤ TA ≤ +125°C 0 1.8 V
Common-Mode Rejection Ratio CMRR 0 V ≤ VCM ≤ 1.8 V 85 100 dB

−40°C ≤ TA ≤ +85°C 85 dB

−40°C ≤ TA ≤ +125°C 80 dB
Large Signal Voltage Gain AVO 0.05 V ≤ V

−40°C ≤ TA ≤ +125°C 95 dB
Offset Voltage Drift

Input Capacitance Differential Mode
Input Capacitance Common Mode

OUTPUT CHARACTERISTICS

Output Voltage High VOH R

−40°C ≤ TA ≤ +125°C 1.78 V
R

−40°C ≤ TA ≤ +125°C 1.65 V
Output Voltage Low VOL R

−40°C ≤ TA ≤ +125°C 5 mV
R

−40°C ≤ TA ≤ +125°C 25 mV
Short-Circuit Limit ISC ±6.5 mA

POWER SUPPLY

Power Supply Rejection Ratio PSRR VSY = 1.8 V to 5 V 100 110 dB

−40°C ≤ TA ≤ +85°C 100 dB

−40°C ≤ TA ≤ +125°C 95 dB
Supply Current per Amplifier ISY V

−40°C ≤ TA ≤ +125°C 25 μA

DYNAMIC PERFORMANCE

Slew Rate SR RL = 100 kΩ, CL = 10 pF, G = 1 13 mV/μs
Gain Bandwidth Product GBP RL = 1 MΩ, CL = 20 pF, G = 1 95 kHz
Phase Margin Φ

NOISE PERFORMANCE

Voltage Noise en p-p f = 0.1 Hz to 10 Hz 2.8 μV p-p
Voltage Noise Density en f = 1 kHz 45 nV/√Hz
Current Noise Density in f = 1 kHz 15 fA/√Hz

ΔV
C

DIFF

CCM

M

OS

/ΔT

−40°C ≤ T
3 pF

4.2 pF

= 100 kΩ to GND 1.78 1.79 V

L

= 10 kΩ to GND 1.65 1.75 V

L

= 100 kΩ to VSY 2 5 mV

L

= 10 kΩ to VSY 12 25 mV

L

= VSY/2 16.5 20 μA

OUT

RL = 1 MΩ, CL = 20 pF, G = 1 60 Degrees

≤ 1.75 V 95 115 dB

OUT

≤ +125°C 2.5 μV/°C

A

Rev. PrA | Page 3 of 4

AD8508 Preliminary Technical Data

www.BDTIC.com/ADI

ABSOLUTE MAXIMUM RATINGS

Table 3.

Parameter Rating

Supply Voltage 5.5 V
Input Voltage ±VSY ± 0.1 V
Input Current1 ±10 mA
Differential Input Voltage2 ±VSY
Output Short-Circuit Duration to GND Indefinite
Storage Temperature Range −65°C to +150°C
Operating Temperature Range −40°C to +125°C
Junction Temperature Range −65°C to +150°C
Lead Temperature (Soldering, 60 sec) 300°C

1

Input pins have clamp diodes to the supply pins. Input current should be

limited to 10 mA or less whenever the input signal exceeds the power
supply rail by 0.5 V.

2

Differential input voltage is limited to 5 V or the supply voltage, whichever

is less.

Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; 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.

THERMAL RESISTANCE

θJA is specified for the worst-case conditions, that is, a device
soldered in a circuit board for surface-mount packages. This
was measured using a standard two-layer board.

Table 4. Thermal Resistance

Package Type θJA θJC Unit

8-Lead MSOP (RM-8) 190 44 °C/W
14-Lead TSSOP (RU-14) 180 35 °C/W

ESD CAUTION

Rev. PrA | Page 4 of 4 PR07524-0-7/08(PrA)