TVG amp

[bob]

Sture,


I was thinking about the TVG amps. On the 100kHz side, there are 2 amps, but on the 500 kHz side, there are 3. Is this because the 500 kHz signal is weaker?


Also, on the 500kHz side, there is C2, a capaicitor in series with the 2nd and third amp. You were saying that an AM radio doesn't go down to DC, but it seems to me that with this cap, the 500kHz amp won't either. Perhaps in the timeframe of a ping, this doesn't come into play..


I was also looking around the net for other variable gain amplifiers. I found some, but few had the ability to work over the 70 db range that these do. Do you recommend any other types? (or should I just stick with these!)


Regardless of the chips I use, what is the maximum number of them I can put in series? It seems to me that if we put a whole bunch in series, then the noise from the first stage will be amplified as well, so only so much gain can be made. What are your thoughts on this??


Thanks very much,


-Bob

[Sture Hultqvist]

Re: TVG amp

Hi


2 or 3 amp? The 500KHz signal is much weaker


and requires higher amplifikation.


DC level is the output after the detector in


the upside electronic and not in the preamp.


In principal it should be possible to rebuild


a radio a little to prevent it from varying its


DC output, or building a buffer amplifier.


Number of amplifiers and noise... you overestimate


my knowledge a bit It should be a low noise


design however the sea itself gives acoustic noise


wich I have found be greater than electronic noise.


Analog Devices have several chips that might be


very useful for sidescans. So far I have not done


any konstructions.


Sture