AD8608 Просмотр технического описания (PDF) - Analog Devices

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производитель

AD8608

Precision, Low Noise, CMOS, Rail-to-Rail, Input/Output Operational Amplifiers

Analog Devices 

AD8605/AD8606/AD8608

Data Sheet

APPLICATIONS INFORMATION

OUTPUT PHASE REVERSAL

Phase reversal is defined as a change in polarity at the output of

the amplifier when a voltage that exceeds the maximum input

common-mode voltage drives the input.

VS = ±2.5V

VIN = 6V p-p

AV = 1

RL = 10kΩ

VOUT

Phase reversal can cause permanent damage to the amplifier; it

VIN

can also cause system lockups in feedback loops. The AD8605

does not exhibit phase reversal even for inputs exceeding the

supply voltage by more than 2 V.

MAXIMUM POWER DISSIPATION

Power dissipated in an IC causes the die temperature to

increase, which can affect the behavior of the IC and the

application circuit performance.

The absolute maximum junction temperature of the AD8605/

AD8606/AD8608 is 150°C. Exceeding this temperature could

damage or destroy the device.

The maximum power dissipation of the amplifier is calculated

according to

PDISS

=

TJ −TA

θ JA

where:

TJ is the junction temperature.

TA is the ambient temperature.

θJA is the junction-to-ambient thermal resistance.

Figure 47 compares the maximum power dissipation with

temperature for the various AD860x family packages.

INPUT OVERVOLTAGE PROTECTION

The AD860x has internal protective circuitry. However, if the

voltage applied at either input exceeds the supplies by more

than 0.5 V, external resistors should be placed in series with

the inputs. The resistor values can be determined by

VIN − VS ≤ 5mA

RS

TIME (4µs/DIV)

Figure 46. No Phase Reversal

1.8

1.7

1.6

SOIC-14

1.5

1.4

1.3

TSSOP-14

1.2

1.1

1.0 SOIC-8

0.9

0.8

0.7

0.6 MSOP-8

0.5

WLCSP-5

0.4

0.3

5-LEAD SOT-23

0.2

0.1

0

–45

–20

5

30

55

80

105

130

AMBIENT TEMPERATURE (°C)

Figure 47. Maximum Power Dissipation vs. Ambient Temperature

0.1

VSY = ±2.5V

AV = 1

BW = 80kHz

0.01

The remarkable low input offset current of the AD860x (<1 pA)

allows the use of larger value resistors. With a 10 kΩ resistor at

the input, the output voltage has less than 10 nV of error voltage.

A 10 kΩ resistor has less than 13 nV/√Hz of thermal noise at

room temperature.

THD + NOISE

Total harmonic distortion is the ratio of the input signal in V rms

to the total harmonics in V rms throughout the spectrum.

Harmonic distortion adds errors to precision measurements

and adds unpleasant sonic artifacts to audio systems.

0.001

0.0001

20

100

1k

FREQUENCY (Hz)

Figure 48. THD + Noise vs. Frequency

10k 20k

The AD860x has a low total harmonic distortion. Figure 48 shows

that the AD8605 has less than 0.005% or −86 dB of THD + N

over the entire audio frequency range. The AD8605 is configured

in positive unity gain, which is the worst case, and with a load

of 10 kΩ.

Rev. O | Page 16 of 24

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