[Amps] Designing the Cleanest Linear with RF Negative Feedback

[Steve Thompson]

wc6w at juno.com wrote:
> Hi Tom,
>    That '5106 is probably for Cable TV use and likely cuts off around 40 MHz (on the low end!).
> 
>    If I recall correctly, some of the general purpose units that go down to a MHz use numbers from CA28XX group.  They come in both single ended and push-pull versions.

CA2820 and 2830 are good ones, 0.5-1W capability and only a couple of 
power line decoupling caps needed. Motorola equilvalents are MHW590 and 
592 - these replaced the TRW parts after Mot bought TRW. Many other 
CA28** or MHW parts will also suit, but some need external chokes or 
transformers. Beware the gain - around 30dB. If you're running about 
1-200mW out for linearity, it means only -10dBm in (ideal if you build 
your own exciter). If you're going to do that, you could consider going 
the whole hog and incorporate polar or cartesian loop feedback.

>    I've seen a few of the 350J's for sale on the web over the years.  I don't believe the demand is very high for those as they have a 26V heater and as such can't be dropped into a 4CX250B socket.  There is also the 4CX600J/JA/JB.

I'd bet that the 'FJ is barely different from a std '350 - just tested 
for linearity under class A. They might be a few dB better than 'any 
old' '350, but I'd be surprised if the difference was more than a few dB 
- not 10 or more.

Steve