THS4031 Datasheet, PDF (31/38 Pages) Texas Instruments – 100-MHz LOW-NOISE HIGH-SPEED AMPLIFIERS

THS4031, THS4032
100-MHz LOW-NOISE HIGH-SPEED AMPLIFIERS
APPLICATION INFORMATION
SLOS224C – JULY 1999 – REVISED APRIL 2000
general PowerPAD™ design considerations (continued)
The next thing to be considered is package constraints. The two sources of heat within an amplifier are
quiescent power and output power. The designer should never forget about the quiescent heat generated within
the device, especially multiamplifier devices. Because these devices have linear output stages (Class A-B),
most of the heat dissipation is at low output voltages with high output currents. Figure 57 to Figure 60 shows
this effect, along with the quiescent heat, with an ambient air temperature of 50°C. When using V_CC = ±5 V, heat
is generally not a problem, even with SOIC packages. But, when using V_CC = ±15 V, the SOIC package is
severely limited in the amount of heat it can dissipate. The other key factor when looking at these graphs is how
the devices are mounted on the PCB. The PowerPAD™ devices are extremely useful for heat dissipation. But,
the device should always be soldered to a copper plane to fully use the heat dissipation properties of the
PowerPAD™. The SOIC package, on the other hand, is highly dependent on how it is mounted on the PCB. As
more trace and copper area is placed around the device, θ_JA decreases and the heat dissipation capability
increases. The currents and voltages shown in these graphs are for the total package. For the dual amplifier
package (THS4032), the sum of the RMS output currents and voltages should be used to choose the proper
package.
THS4031
MAXIMUM RMS OUTPUT CURRENT
vs
RMS OUTPUT VOLTAGE DUE TO THERMAL LIMITS
200
VCC = ± 5 V
180 ^{TJ = 150°C}
TA = 50°C
160
Maximum Output
Current Limit Line
140
120
100
80
SO-8 Package
θ_JA = 167°C/W
60 ^{Low-K Test PCB}
Package With
θ_JA < = 120°C/W
40
20
Safe Operating
Area
0
0
1
2
3
4
5
| VO | – RMS Output Voltage – V
Figure 57
THS4031
MAXIMUM RMS OUTPUT CURRENT
vs
RMS OUTPUT VOLTAGE DUE TO THERMAL LIMITS
1000
TJ = 150°C
TA = 50°C
VCC = ± 15 V
DGN Package
θ_JA = 58.4°C/W
Maximum Output
Current Limit Line
100
SO-8 Package
θ_JA = 98°C/W
High-K Test PCB
SO-8 Package
10
0
θ_JA = 167°C/W
Low-K Test PCB
Safe Operating
Area
3
6
9
12
15
| VO | – RMS Output Voltage – V
Figure 58
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