[sdiy] Op-amp to boost VC signal with +5V/GND?

[René Schmitz]

Hi Mykolas,

mikas schrieb:
> Hi guys,
> 
> My project is slowly moving forward.
> http://www.analogas.uzrasai.lt/tag/seq/ ( LT at the moment only, EN
> coming soon).
> 
> 1. Could You recommend me an op-amp to boost VC signal with single
> +5V/GND power supply? I don't want to make PSU with +12V/gnd/-12V (or
> 15V) just for boosting VC signal. I've made simple +5V with 7805 to
> use with external +8V PSU. I want to keep it simple.
> 
> http://www.analogas.uzrasai.lt/wp-content/uploads/2010/07/seq1.jpg
> 
> Can I use TLC27? Or other recomendations. My local shops are a bit
> limited, ex: http://www.rcl.lt/index.php?id=2&lang=en&acc=show&fid=644

They should be fine, if you power them from your 8V supply. That ensures 
that you can get output up to 5V. (They can't hit the positive rail.)

Looking at your schematic, one additional remark: I would change that 
arrangement for the portamento. As shown you charge up that 22u cap 
directly from the multiplexer when you have switched porta off. That 
could mean a high current through the multiplexer. I would put a 1k or 
so resistor between the cap and the + input of the opamp. The "off" 
coming from the switch going to the + input directly.

> 2. Also, can I drive GATE with two 40106 as shown in schematics? Idea
> taken from MFOS.

Yes.

Cheers,
  René

-- 
uzs159 at uni-bonn.de
http://www.uni-bonn.de/~uzs159