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This data sheet has been carefully checked and is believed to be reliable, however, no responsibility is assumed for possible inaccuracies or omissions. All specifications are subject to change without notice.

PA98U REV I DECEMBER 2004 © 2004 Apex Microtechnology Corp.

OPERATING

CONSIDERATIONS

PA98 • PA98A

INTERNAL POWER DISSIPATION AND HEATSINK SELECTION

With the unique combination of high voltage and speed

of the PA98, traditional formulas for heatsink selection will

falsely lower the apparent power handling capability of this

amplifier. To more accurately predict operating temperatures

procedure:

Find internal dissipation (PD) resulting from driving the

load. Use Power Design or refer to Apex Applications Note

1, General Operating Considertaions, paragraph 7. Find total

quiescent power (PD

supply voltage). Find output stage quiescent power (PD

by multiplying 0.001 by V

Calculate a heatsink rating which will maintain the case at

85°C or lower.

Where: T

T

Calculate a heatsink rating which will maintain output transistor

junctions at 150°C or lower.

Where: T

R

tion table.

Use the larger heatsink of these two calculations.

Power Design is an Excel spreadsheet available free from

www.apexmicrotech.com

Tc - Ta

R

-0.1°C/W

PD + PD

Q

T

R

-0.1°C/W

PD + PD

Q