Re: Change impedance

Posted by IvIark on Jul 21, 2014; 9:25pm
URL: http://guitar-fx-layouts.238.s1.nabble.com/Change-impedance-tp11695p11704.html

It's the virtual ground reference voltage that is used in most opamp circuits that use a simple 9V supply.  You'll often see an area in a schematic with one 10K (for instance) resistor going to the supply and another 10K resistor going to ground.  That makes a voltage divider based on the ratio between the resistor values, and when the values are both identical you end up with 4.5V from a 9V supply.  You'll often see it marked up as vbias, vref, 1/2 supply or 4.5V on the schematics.  And it just gives a central reference point between 9V and ground.

It's basically simulating a bipolar supply which may be +/-9V which then uses true ground as the central reference (half way between -9V and +9V).