Hello,I have a question about harmonic distortion of ADL5565 from our customer.It's about figure-21 of the datasheet(Rev.G)(He is using VPOS=3.3V and single-end input)The HD3 is about 12dB degraded relative to figure-17 at F=250MHz and Av=5.3dB.(At Av=10.3dB and 13dB, the HD3 is not degraded relative to figure-17)And HD2 is about 20dB degraded relative to figure-17 at F=250MHz and Av=5.3dB.The customer feel wonder that the degradation of HD2 is too large than HD3.Would you teach me the reason of this ?Best regards,y-suzuki
Hi y-suzuki,
The ADL5565 provides three gain levels of 6 dB, 12 dB, and 15.5 dB through a pin strappable configuration.
For the singleended input configuration, the gains are reduced to 5.3 dB,10.3 dB…
For the singleended input configuration, the gains are reduced to 5.3 dB,10.3 dB, and 13 dB. Using two external series resistors expands
the gain flexibility of the amplifier and allows for any gain selection from 0 dB to 15.5 dB for a differential input and 0 dB
to 13 dB for a single-ended input.
The input of the device can be configured as single-ended or differential with similar third-order distortion performance. Due to the
internal connections between the inputs and outputs, an output common-mode voltage between 1.4 V and 1.8 V at 3.3 V and
1.4 V to 3 V at 5 V must be maintained for the best distortion.
Although distortion is similar over the specified frequency range at both 3.3 V and 5 V, lower distortion results on the 5 V supply for signal swings larger than 2 V p-p.
If the inputs are ac-coupled, the input and output common-mode voltages are set by VCC/2 when no external circuitry is used.
For a dc-coupled input, the input common mode should be between 1.2 V and 2 V at the 3.3 V supply, and 1.2 V to 3.8 V at
the 5 V supply.
Hope this helps
Warm Regards,
rachana