[sdiy] Voltage regs + diode drops.

[Ian Fritz]

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.  :-)

Ian