[sdiy] Voltage regs + diode drops.

[Dave Manley]

Ian Fritz wrote:
> At 08:31 AM 2/21/2009, Dave Kendall wrote:
>
>> Is there any good reason not to use diodes in series after the output 
>> terminal of a positive voltage regulator to get odd voltages, eg. 2 x 
>> 1N4001 after a LM7809 to get just below +8V?
>
> No reason at all!  I do stuff like that all the time.  Of course you 
> do have to worry about loading and temperature effects, so there are 
> some limitations, but in general it's a very useful trick to have in 
> your bag.
>
> Here's a link to my latest Saw VCO core:
> http://electro-music.com/forum/topic-28713-25.html  (scroll down)
> D5 reduces the PS voltage for A3 for reduced power consumption and 
> increased speed.  D2 and D3 provide accurate and stable sub-regulated 
> reference voltages.
>
> Here's my Tri VCO with (a) 3 diodes in series providing a 2 V supply 
> level for the current switch (D1-D3), (b) 2 Zeners used as series 
> regulators to power the comparators (D6, D9), and (c) 2 more Zeners 
> for stable reference voltages.
> http://home.comcast.net/~ijfritz/sy_cir4.htm
>
> Just a couple of examples.  :-)
>
For another example the Serge ASR uses diode drops for local supplies:

http://www.cyndustries.com/synapse/synapse.cfm?pc=35&folder=sept1976&pic=31

The article starts here if you want to read the whole thing:

http://www.cyndustries.com/synapse/synapse.cfm?pc=35&folder=sept1976&pic=19

-Dave