active antenna LNA
active antenna LNA
(OP)
I am designing a active antenna (100KHz). Can I use AD 797 (ultra LNA) as the amp instead of JFET. the input output impedance of this opamp are similar to that of JFET (high input imp and low output imp).
I have not seen any design implementing opamp in active antenna and was curious if there are any problems.
I have not seen any design implementing opamp in active antenna and was curious if there are any problems.





RE: active antenna LNA
The gain is down to 60 dB at 100 KHz; though the phase margin still looks good. How much gain do you need?
Op amps get a lot of use as transimpedance amps. There are some good books out there that you might reference.
On the other hand...
You might find better data for the input impedance of a FET; the op-amp will require experimentation.
RE: active antenna LNA
RE: active antenna LNA
I note that the designers of Active Antennas always take great pains to keep the antenna element away from ground. The whip is always mounted directly in a manner (how can I put it?...) diametrically opposed to feeding it through a length of coax.
The input impedance, both R and C, needs to be extreme (high R, low C).
RE: active antenna LNA
RE: active antenna LNA
I've got two around the house, a Sony AN-1 (broadband) and an MJF-1020A (tuned). They work 'hotdamn' on VLF to HF. But they do not offer any directionality as a small loop might.