THS4011, THS4012

290-MHz LOW-DISTORTION HIGH-SPEED AMPLIFIERS

SLOS216B – JUNE 1999 – FEBRUARY 2000

23

POST OFFICE BOX 655303

APPLICATION INFORMATION

general PowerPAD design considerations (continued)

The next consideration is the 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 muti-amplifier 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 36 to Figure 39 show this effect,

along with the quiescent heat, with an ambient air temperature of 50

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,

increases. The currents and voltages shown in these graphs are for the total package. For the dual amplifier

package (THS4012), the sum of the RMS output currents and voltages should be used to choose the proper

package.

Figure 36

Package With

θJA < = 120°C/W

SO-8 Package

θJA = 167°C/W

Low-K Test PCB

VCC = ± 5 V

Tj = 150°C

TA = 50°C

100

80

40

0

01

2

3

140

180

200

45

160

120

60

20

| VO | – RMS Output Voltage – V

Maximum Output

Current Limit Line

THS4011

MAXIMUM RMS OUTPUT CURRENT

vs

RMS OUTPUT VOLTAGE DUE TO THERMAL LIMITS

Safe Operating

Area

Figure 37

100

10

03

6

9

1000

12

15

Maximum Output

Current Limit Line

SO-8 Package

θJA = 167°C/W

Low-K Test PCB

SO-8 Package

θJA = 98°C/W

High-K Test PCB

TJ = 150°C

TA = 50°C

| VO | – RMS Output Voltage – V

VCC = ± 15 V

DGN Package

θJA = 58.4°C/W

THS4011

MAXIMUM RMS OUTPUT CURRENT

vs

RMS OUTPUT VOLTAGE DUE TO THERMAL LIMITS

Safe Operating

Area