Hi,

I have read in one article in analogue dialogue that voltage gain of device is 5.9dB when load is 200Ohm, and it is changed to 6.9dB when load is 450Ohm(which is also mentioned in datasheet).

My question is does voltage gain increases if we increase load above 450Ohm, i.e. does output stage of ADL5380 behave like constant current source?

Regards,

Dwijen

Hello Dwijen,

I believe your understanding is correct. The gain quoted on the datasheet is a voltage gain and not a power gain. The peak ouptut current of the ADL5380 is 12 mA. Voltage gain will increase with increasing load however you also need to take into consideration the losses due to the impedance mismatch. The I and Q output impedance of the ADL5380 is 50 ohms and you would want to terminate the device with 200 or 450 ohms. When terminating the device with 200 ohms, you'll get 10 log (50/200) = -6 dB of loss; therefore resulting in almost no voltage gain. It is important to take the output impedances into consideration when working with voltage gains.

Qui