### Calculating maximum power delivered to load for current

```Calculating maximum power
steering DACs
1
Calculations
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Calculate the peak-to-peak voltage at the output of the DAC
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Find voltage at load by dividing by the sqrt of the impedance ratio
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Calculate power DELIVERED to the load
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Where sqrt(Nimp) = 2 for 4:1 trans, 1.414 for 2:1 trans, 1 for 1:1 trans
Convert peak-to-peak voltage to rms voltage
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Vdacp-p = IFS * R
Where R is the total impedance seen by the DAC and IFS is the full-scale
output current
RL is the impedance after the transformer, probably 50 ohms such as in
the case of a spectrum analyzer hooked up to the transformer output
Convert power to dBm
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PdBm = 10 * log(Pload / 1 mW)
2
Example 1:1 transformer
Vdacp-p = (20 mA) * ((50+50) // 100 // 50) = 500 mV (25 ohm total load)
Vloadp-p = 500 mV / sqrt(1) = 500 mV
Vloadrms = 500 mV / (2 * sqrt(2) ) = 176.8 mV
Pload = (176.8 mV)2 / 50 = 625.2 uW (spectrum analyzer = 50 ohm load)
PdBm = 10 * log(625.2 uW / 1 mW) = -2.04 dBm
3
Example 2:1 transformer
Vdacp-p = (20 mA) * ((50+50) // (2*50)) = 1 V (50 ohm total load)
Vloadp-p = 1 V / sqrt(2) = 707.2 mV
Vloadrms = 707.2 mV / (2 * sqrt(2) ) = 250 mV
Pload = (250 mV)2 / 50 = 1.25 mW (spectrum analyzer = 50 ohm load)
PdBm = 10 * log(1.25 mW / 1 mW) = 0.969 dBm
4
Example 4:1 transformer
Vdacp-p = (20 mA) * ((100+100) // (4*50)) = 2 V (100 ohm total load)
Vloadp-p = 2 V / sqrt(4) = 1 V
Vloadrms = 1 V / (2 * sqrt(2) ) = 353.6 mV
Pload = (353.6 mV)2 / 50 = 2.5 mW (spectrum analyzer = 50 ohm load)
PdBm = 10 * log(2.5 mW / 1 mW) = 3.98 dBm
5
```