>> >I have to agree with Peter, I can't imagine a 723 being a "good
>> >choice" for an IC near strong RF fields.
>>
>> Instead of trying to imagine, why not try trying to see if it works, Mr.
>> Rauch?
>
>I've had bad luck with 723's unless they are in a well shielded
>area and everything is bypassed quite well.
I believe that the circuit designer designs his own luck.
>The shielding and layout is probably more important than the
>specific value of bypass component, especially since the series
>resonant frequency varies greatly with different components and lead
>lengths.
That's why solid state RF amplifiers typically use multi-values multi-C
DC supply RF byassing. That's why I used it in my 723-based screen
supply. I know that if you have RF on V-in, you are IN trouble.
>Time would be better spent describing a proper layout and
>bypassing, especially since Peter is right. The 723 is very
>sensitive to EMI (even from HF).
The 723-based screen regulator described on my Web site ...
http://www.vcnet.com/measures
... works satisfactorily in the presence of RF. I use it in my 8169 AB1
amplifier. The screen regulator is virtually RF-proof even though it is
minimally shielded. The trick was to add enough R to the 723'a
non-inverting input pin to prevent RFI to the extraordinarily high I-gain
error-amplifier and comparitor.
......
>The refrigerator and air conditioner start at the same time, the
>lights flicker, the filament drops to 4.65 volts for just a second,
>and you now have to wait wait three minutes to talk.
This would not happen if the designer added a c. 2-sec. R/C delay to the
sampler.
....
>....... This seems like a case of "do it my way, it's the only right
>way".
>
It was the only way I found that the 723 could pass the Joel/N6AMG RFI
test . More gain is not always better.
- Rich -
R. L. Measures, 805-386-3734, AG6K
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