Data Sheet

©2007-2013 Exar Corporation

14/17

Rev 1G

2

+

2

+

2

1 +

R

f

R

g

2

2

R

f

R

g

2

2

external resistor noise terms for Rs, Rg and Rf

High source impedances are sometimes unavoidable, but

they increase noise from the source impedance and also

make the circuit more sensitive to the op amp current

noise. Analyze all noise sources in the circuit, not just the

op amp itself, to achieve low noise in your application.

Power Dissipation

Power dissipation should not be a factor when operating

under the stated 500Ω load condition. However,

applications with low impedance, DC coupled

loads

should be analyzed to ensure that maximum allowed

junction temperature is not exceeded. Guidelines listed

below can be used to verify that the particular application

will not cause the device to operate beyond it’s intended

operating range.

Maximum power levels are set by the absolute maximum

junction rating of 150°C. To calculate the junction

temperature, the package thermal resistance value

dissipation.

needs to be subtracted from the total power delivered by

the supplies.

Supply power is calculated by the standard power

equation.

Power delivered to a purely resistive load is:

the effect of the feedback network. For instance,

These measurements are basic and are relatively easy to

perform with standard lab equipment. For design purposes

however, prior knowledge of actual signal levels and load

impedance is needed to determine the dissipated power.

power can be calculated as above with the desired signal

amplitudes using:

The dynamic power is focused primarily within the output

stage driving the load. This value can be calculated as:

Assuming the load is referenced in the middle of the

Figure 4 shows the maximum safe power dissipation in the

package vs. the ambient temperature for the packages

available.

0

0.5

1

1.5

2

2.5

-40

-20

0

20

40

60

80

100

120

Ambient Temperature (°C)

SOT23-6

SOIC-8

Figure 4. Maximum Power Derating