Data Sheet
perature, the package thermal resistance value Theta
Application Information
JA
(Ө ) is used along with the total die power dissipation.
JA
Basic Operation
T
= T
+ (Ө × P )
Junction
Ambient JA D
Figures 1 and 2 illustrate typical circuit configurations for
non-inverting, inverting, and unity gain topologies for dual
supply applications. They show the recommended bypass
capacitor values and overall closed loop gain equations.
Where T
is the temperature of the working environment.
Ambient
In order to determine P , the power dissipated in the load
needs to be subtracted from the total power delivered by
D
the supplies.
+Vs
6.8μF
P = P
- P
load
D
supply
Supply power is calculated by the standard power equa-
0.1μF
tion.
Input
+
-
Output
P
= V
× I
supply
supply RMS supply
RL
V
= V - V
S+ S-
supply
0.1μF
6.8μF
Rf
Power delivered to a purely resistive load is:
Rg
2
P
= ((V
)
)/Rload
eff
load
LOAD RMS
G = 1 + (Rf/Rg)
-Vs
The effective load resistor (Rload ) will need to include
eff
the effect of the feedback network. For instance,
Figure 1. Typical Non-Inverting Gain Circuit
Rload in figure 3 would be calculated as:
eff
+Vs
6.8μF
R || (R + R )
L
f
g
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.
R1
0.1μF
+
Output
Rg
Input
-
RL
Here, P can be found from
0.1μF
D
Rf
P = P
+ P
- P
D
Quiescent
Dynamic Load
6.8μF
G = - (Rf/Rg)
-Vs
Quiescent power can be derived from the specified I val-
ues along with known supply voltage, V
S
For optimum input offset
voltage set R1 = Rf || Rg
. Load power
Supply
can be calculated as above with the desired signal ampli-
tudes using:
Figure 2. Typical Inverting Gain Circuit
(V
)
= V
/ √2
LOAD RMS
PEAK
Power Dissipation
( I
)
= ( V
)
/ Rload
LOAD RMS
LOAD RMS eff
Power dissipation should not be a factor when operating
under the stated 1000 ohm load condition. However, ap-
plications 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 operat-
ing range.
The dynamic power is focused primarily within the output
stage driving the load. This value can be calculated as:
P
= (V - V
)
× ( I )
LOAD RMS
DYNAMIC
S+
LOAD RMS
Assuming the load is referenced in the middle of the pow-
er rails or V /2.
supply
Figure 3 shows the maximum safe power dissipation in
the package vs. the ambient temperature for the pack-
ages available.
Maximum power levels are set by the absolute maximum
junction rating of 150°C. To calculate the junction tem-
©2007-2008 CADEKA Microcircuits LLC
www.cadeka.com
15
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