Question: I've been looking at various RF power detectors for a project I'm working on, but I don't quite understand what the manufacturers mean by "dB range".

For example, the [LT5534](http://cds.linear.com/docs/en/datasheet/5534fc.pdf) Log RF Power Detector has a frequency range of 50 MHz - 3 GHz; the minimum it can detect is -63dB and the maximum is 2 dB. What does that mean?

Answer: 
The minimum and maximum levels are determined by the linearity and noise floor of the amplifier. Anything under -63 dBm in this case isn't reliably detectable because the amplifier generates noise on its output that looks like -63 dBm on its input. Anything over -2 dBm gets clipped or distorted, so it can't be measured reliably. Say, if you put a -80 dBm signal in, the output will look like you put in a -63 dBm signal. Or if you put in a +2 dBm signal, the output might say you are putting in a -1 dBm signal. 

The frequency range is the range of RF frequencies that it can detect. Generally there are filters and what not to limit the range of detectable frequencies. It also depends on the design of the power detector itself. Anything under 50 MHz or over 3 GHz will either not be detected at all, or they will be detected at a lower sensitivity than signals within the range. For example, if you put a 4 GHz signal in at -10 dBm, the chip might read it at -20 dBm.
-63 dBm is roughly equivalent to 1 nano Watts
while 
-2 dBm is equivalent to 0.6 milliwatts

All it says is that the device has 61dB (-63dbm minus -2dBm) dynamic range (power range where it will provide linear and correct measurements) and it overloads once you feed it above -2dBm or 0.6 milliwatts.

here is the transfer curve

![enter image description here](https://i.stack.imgur.com/Sto7P.jpg)

Your Vout will register 0.2V if you feed it -60dBm signal bet (50MHz to 3GHz)
while Vout will register near 2.4V(maybe 2.39xxxxxV) if you feed it -2dBm signal bet (50MHz to 3GHz)