i have some queries about AD8309. i want to use it for logarithmic amplification with its limiter output.
when i read the datasheet, it shows the gain should be 72dB(six-stage total gain) + 18dB=90dB. my first questions are:
1, does it mean the gain is 90dB if used? it is quite big... my input is -40dBm~+10dBm. is it possible for logarithmic amplification with AD8309's limiter output function?
2, if so, what is the output power level?
i used to use AD83XX as log detector. now i need logarithmic amplification for my product. so i choose AD8309 due to its limiter function. but i am not sure whether it is proper... and need your help.
i am a rookie for such application and thanks in advance for your kindly help!
1) It is 90 if the limiter amps are not limiting; if a limiter stage is limiting, then the gain is 0 dB for that stage.
What do you mean by "logarithmic amplification"? Do you mean instantaneous log of the input? Either way, the limiter output does not give any log information. For that you need to monitor the VLOG pin.
2) When the signal is limited at the output, its level is about 100 mV pp.
Let me know a little bit more about your application and I can then help you to decide whether the AD8309 is correct for you or not.
thanks so much for your kindly help!
i want to select an amplifier. when input low level signal, it has high gain; when input high level signal, it has low gain. the transfer function is logarithmic curve.
How about one of our VGAs? AD8367, AD8368, or ADL5336?
Are you trying to do an AGC loop?