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In the specification section for 140Mhz OIP3 is +39dBm for AV = 15.5 dB, RL = 200 Ω, VOUT = 2 V p-p composite (2 MHz spacing), but figure 13 shows another results. Why it is so ?

In my point of view 2 V p-p composite (RL=200Ohm diff or not ?) = 4dBm per tone ? And what the difference between   2 V p-p composite  and 2 V p-p envelope? ## Top Replies

• Hi,

For the ADL5561 and similar parts, because they are specified with a 200-ohm load, the dBm specifications are with reference to this impedance and not 50-ohms.

Yes, composite is the same as envelope.  So 2Vpp composite is 1Vpp/tone for a two-tone sinewave test

1. However, because the part is specified with a 200-ohm load, Pout(dBm)/TONE is calculated as 10*log10(0.5*0.5/2/200/1m) = -2dBm
1. Note: OIP3 in dBm is also plotted with reference to a 200-ohm impedance

This does make the number for OIP3 in the specification table look a little conservative.

OIP3 = 39dBm

IMD3 = -96dBc

If the numbers above are correct, then OIP3 from IMD3 would be

-2dBm(200) + 96/2 = 46dBm(200)   vs 39dBm specified in the specification table.

IMD3 = -96dBc looks reasonable from Figure 12, but I cannot figure out how 39dBm was arrived at.

Warm Regards,

Rachana

• Thank you for your explanation!