[Amps] Bias Zener Diodes In Parallel ?

[2]

>>What is the cost in quid [£] of the TL431-TIP147 circuit ?
>>
>
>You can have it in green stamps: under $5.
>
**  Not bad.

>For that, you get: adjustable voltage from 5V to 40V, all the current 
>capability you need, better regulation than you'd ever need, and EBS 
>capability. The same $5-worth can handle anything up to a YC156.
>
**  Sounds good.

>Compare with a 20W stud-mounted zener at $10 over here (and it ain't big 
>enough) or a 75W one for $25... for one fixed voltage.

>I didn't include a heat sink in the calculations, but either solution 
>would require that.
>
**  Agreed, although a 3A diode string requires no heat sink.

>For cheapness, neither the active regulator nor zeners can compete with 
>a string of diodes... but frankly that's a competition neither Paul nor 
>I would want to be involved in.
>
**   You believe a fraction of a volt of RF-NFB is not ok?
>
>>>and glitch resistance.
>>
>>What is the I-peak withstanding ability of TL431-TIP147 circuit?
>>
>More than you need. With the grid directly grounded and the meters 
>protected by diodes (as recommended by Rich), none of the glitch current 
>actually goes through the cathode bias circuit anyhow.
>
**  During an HV- to gnd arc, no  --  but during a VHF/UHF parasite, an 
8877 is capqable of  >50A-pk  cathode current (Ik).  However, 50A would 
torpedo a 10A transistor (Q1).

>But just to be sure, I routinely test my amplifiers by dropping a wrench 
>into the anode compartment. They shut down automatically with no drama 
>and no damage, not even a blown fuse... no fun at all, really.
>
**  Excellent.  Murphy would no doubt approve. 
>
cheers,  Ian

-  R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K, 
www.vcnet.com/measures.  
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