FAQ: ADL5801 Low Frequency Operation

Document created by MickOC Employee on Jul 8, 2011Last modified by AndyR on Jan 31, 2012
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The ADL5801 datasheet states that the device is capable of operation to frequencies as low as 10 MHz, yet the Typical Performance Characteristics plots only show data as low as 500 MHz. Is the device capable of operation at these low frequencies and is there any typical performance data available?




The ADL5801 is indeed capable of operating at frequencies as low as 10 MHz. In order to achieve low frequency operation some changes are necessary to the standard evaluation board. Specifically, the RF & LO series input capacitors (C4, C5, C8 & C9) should be changed from  their datasheet recommended value of 5.3pF & 100pF to a higher value of 1nF. The lower capacitor values create a highpass filter effect on the input resulting in poor return loss at low frequency which should be avoided.


The performance of the ADL5801 was characterized for IF frequencies of 10 MHz and 70 MHz in Low Side LO and High Side LO configurations. The typical performance of the ADL5801 can be seen in the attached plots.


The standard ADL5801 evaluation board configuration was used. Capacitors C4, C5, C8 & C9 were replaced with 1nF capacitors. VS=5V, VSET=3.8V, unless otherwise noted. The 4:1 IF port transformer (TC4-1W+), the RF and LO port transformers ( TC1-1-13M+) and PCB loss are included in the measurement.


Summary: The ADL5801 under low frequencies indicates the following typical performance: Gain = 0dB (Balun and PCB loss inclusive), IIP3 = 30dBm, IIP2 = 70dBm, P1dB = 11dBm and Noise Figure = 12dB.