Op amps may very well be a good solution for a very linear amplifier. However, my point is how many current amateur radios use this much more expensive solution in their audio chains? My transceivers are dated, as I suspect many hams are, but not so old that they couldn't have used op amps for a very fine wide bandwidth amp. I'll be honest, I also don't know what kind of phase shift problems op amps will have even if the amplitude variations are minimized. On the other hand, it has been a while since I investigated op amps and they had some issues. At the time, there were none offered that could deal adequately with a balanced modulator (RF mixer) either because of the toroids used in a balanced modulator nor could they provide the +7 dBm or higher powers needed for this purpose. Bipolars were the best solution for this type of need. In addition, power supply requirements, i.e., +12/-12 volts to get good common mode rejection was also needed. Jim WA0LYK --- In digitalradio@yahoogroups.com, "Jose A. Amador" <[EMAIL PROTECTED]> wrote: > > jgorman01 wrote: > > > Just a quick example. In order to achieve a flat passband of 3 kHz > > you may really need an amplifier whose bandwidth is 10 or even 20 > > kHz. To achieve this, you probably can't use just one single stage of > > audio amplification with a simple emitter bypass electrolytic > > capacitor, you'll need several stages of Class A (both DC and AC bias > > stabilized) thereby raising the costs significantly. Precision > > components will be used rather than run of the mill 10% tolerance. It > > all adds up both in cost and performance. > > > > Jim WA0LYK > > > I am afraid we are aiming at different solutions. > > I wouldn't use bipolars, I would use op amps. Well used, you would incur > in less than > 0.1 % distortion, and I am afraid it is much more than what it would > deliver. I have > achieved in practice distortions in the order of 0.05% or less for pro > audio designs. > > With op amps, you just decide the corner frequencies, and the gain you > want. Of course, > you must consider the open loop gain and the unity gain frequency. The > rest is choosing > the right resistor values. The rest of the engineering needed is already > included inside > the chip. > > And unless you are working with balanced, matched amplifiers, a fraction > of a dB goes > nowhere. So, 10% resistors are perfectly adequate. > > I would avoid aluminum foil electrolytics. Those are the quickest aging > and most prone > to fail components in a properly done design. > > > 73 de Jose, CO2JA > > > > > > > > > > > > > > > > > > __________________________________________ > > XIII Convención Científica de Ingeniería y Arquitectura > 28/noviembre al 1/diciembre de 2006 > Cujae, Ciudad de la Habana, Cuba > http://www.cujae.edu.cu/eventos/convencion >
Need a Digital mode QSO? Connect to Telnet://cluster.dynalias.org Other areas of interest: The MixW Reflector : http://groups.yahoo.com/group/themixwgroup/ DigiPol: http://groups.yahoo.com/group/Digipol (band plan policy discussion) Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/digitalradio/join (Yahoo! ID required) <*> To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
