AD8605/AD8606/AD8608

Data Sheet

Rev. N | Page 16 of 24

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.

Phase reversal can cause permanent damage to the amplifier; it

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

JA

A

J

DISS

T

T

P

θ

−

=

where:

Figure 45 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

mA

5

≤

−

S

S

IN

R

V

V

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.

The AD860x has a low total harmonic distortion. Figure 46 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.

TIME (4µs/DIV)

Figure 44. No Phase Reversal

AMBIENT TEMPERATURE (°C)

1.0

0.8

0

–45

130

–20

30

80

105

0.6

0.4

0.2

1.7

1.8

1.6

1.4

1.2

TSSOP-14

5

55

1.5

1.3

1.1

0.9

0.7

0.5

0.3

0.1

5-LEAD SOT-23

MSOP-8

SOIC-14

WLCSP-5

SOIC-8

Figure 45. Maximum Power Dissipation vs. Ambient Temperature

FREQUENCY (Hz)

0.1

0.01

0.0001

20

20k

100

1k

0.001

10k

Figure 46. THD + Noise vs. Frequency