[ARC5] Power Supply Filter Question

[Fuqua, Bill L]

   This does not work most of the time  unless you have a leaky capacitor to ground.
The collector to base voltage will be zero. You need a voltage divider to assure 
a reasonable collector to base voltage,ie a resistor to ground.
73
Bill wa4lav

________________________________________
From: arc5-bounces at mailman.qth.net [arc5-bounces at mailman.qth.net] on behalf of Mike Feher [n4fs at eozinc.com]
Sent: Sunday, December 22, 2013 2:28 PM
To: jfor at quikus.com; 'Ben Hall'
Cc: arc5 at mailman.qth.net
Subject: Re: [ARC5] Power Supply Filter Question

If I remember right, this is known as the Miller effect. - Mike

Mike B. Feher, N4FS
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960

-----Original Message-----
From: arc5-bounces at mailman.qth.net [mailto:arc5-bounces at mailman.qth.net] On
Behalf Of J. Forster
Sent: Sunday, December 22, 2013 2:09 PM
To: Ben Hall
Cc: arc5 at mailman.qth.net
Subject: Re: [ARC5] Power Supply Filter Question

It's basically an emitter follower.

The pass traqnsistor's collector goes to the supply; the emitter to the
load.

One version uses a resistor between coll. and base & a capaciytor to ground.
This filters ripple, but does not regulate. It effective capacitance is
roughly beta x cap value.

Another version uses the same resistor position, and one or more zeners in
place of the cap. This regulates the output voltage.

-John

===============





> Hi John and list,
>
> Sounds very interesting.  Where can I find information on the Beta-C
> filter?
>
> On 12/21/2013 7:37 PM, J. Forster wrote:
>> A Beta-C filter is relative simple and more than adequate. With a
>> couple of protective diodes, it's just about bulletproof. The version
>> with a Zener will easily add sufficient regulation.
>
> thanks,
> ben
>
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