>-----Original Message-----
>From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] 
>On Behalf Of Tamas Rudnai
>Sent: 31 October 2007 14:32
>To: Microcontroller discussion list - Public.
>Subject: [EE] Amplified diode regulator
>
>
>Hi,
>
>I was thinking about regulating the Vdd using an amplified 
>diode circuit. Basically the input voltage could be varied 
>between 4-7.2V and I am going to set this circuit to 3.3V. The 
>load is around 1-2mA. I was wondering if there is any con about this?
>
>Thanks,
>Tamas
>

For a tradional amplified diode arangement, the top of R2 should be connected to the collector of the transistor.

The disadvantages are the same as zener diodes, soft knee (poor line and load regulation) and poor tempco etc. but typicaly somewhat worse again.

A linear pass regulator is very likely a better solution.  They are cheap and their performance will be in a different league.

Regards

Mike

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