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Data Sheet

AD8016

Rev. C | Page 17 of 20

Once an optimum turns ratio is determined, the amplifier has

an MTPR performance for each setting of the power-down

pins. Table 8 demonstrates the effects of reducing the total

power dissipated by using the PWDN pins on MTPR perfor-

mance when driving 20.4 dBm downstream onto the line with

a transformer turns ratio of 1:1.4.

Table 8. Dynamic Power Dissipation of Downstream

Transmission

PWDN1

PWDN0

PD (W)

MTPR

1.454

−78 dBc

1.262

−75.3 dBc

1.142

−57.2 dBc

0.120

N/A

This mode is quiescent power dissipation.

GENERATING DMT

At this time, DMT modulated waveforms are not typically

menu selectable items contained within arbitrary waveform

generators. Even using AWG software to generate DMT signals,

AWGs that are available today may not deliver DMT signals

sufficient in performance with regard to MTPR due to limita-

tions in the DAC and output drivers used by AWG manufacturers.

Similar to evaluating single-tone distortion performance of an

amplifier, MTPR evaluation requires a DMT signal generator

capable of delivering MTPR performance better than that of

the driver under evaluation.

POWER DISSIPATION

To properly size the heat sinking area for the user’s application,

it is important to consider the total power dissipation of the

AD8016. The dc power dissipation for VIN = 0 V is IQ (VCC −

VEE), or 2 × IQ × VS.

For the AD8016 powered on +12 V and −12 V supplies (±VS),

the number is 0.6 W. In a differential driver circuit (Figure 41),

one can use symmetry to simplify the computation for a dc

input signal.

OUT

)

(

−

where:

VOUT is the peak output voltage of an amplifier.

This formula is slightly pessimistic due to the fact that some of

the quiescent supply current is commutated during sourcing or

sinking current into the load. For a sine wave source, integra-

tion over a half cycle yields













−

OUT

The situation is more complicated with a complex modulated

signal. In the case of a DMT signal, taking the equivalent sine

wave power overestimates the power dissipation by ~23%. For

example:

POUT = 23.4 dBm = 220 mW

VOUT @ 50 Ω = 3.31 V rms

VOUT = 2.354 V

at each amplifier output, which yields a PD of 1.81 W.

Through measurement, a DMT signal of 23.4 dBm requires

1.47 W of power to be dissipated by the AD8016. Figure 46

shows the results of calculation and actual measurements

detailing the relationship between the power dissipated by

the AD8016 vs. the total output power delivered to the back

termination resistors and the load combined. A 1:2 transformer

turns ratio was used in the calculations and measurements.

Figure 46. Power Dissipation vs. Output Power (Including Back

Terminations), See Figure 9 for Test Circuit

OUTPUT POWER (mW)

2.5

2.0

1.5

100

200

300

1.0

0.5

MEASURED

SINE

MEASURED

DMT

CALCULATED

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