I'm working on a 9V VCO (synthesiser) that has three op amps, of which two needs virtual ground. So far I've been using voltage divider with a couple of caps and it works. I wonder if I need a separate power supply for each op amp? Is the TLE2426 any better? Do I need two of the TLE2426 for the two op amps?
Split power supply for a multiple op amp circuit
analogoperational-amplifier
Related Solutions
R3 connects to the half rail supply but consider that it could be on its own half rail supply - instead of using one 8k2 for R3, use two 16k4 (or nearest preferred value); one down to ground and one up to 9V.
Ditto R11 - it can become two 16k2 resistors in the same way. The two half-rail generators are now independant.
About noise and interference
The proposal I've made will neither improve nor reduce the effects of noise and fluctuations on the 9V power supply. However this type of design could benefit from 100uF decoupling caps on the 9V near these chips.
If you have +5V and -5V then half way between supply voltages is 0V i.e. the common connection of the two batteries - this should be regarded as your "ground" (or 0V) for your circuit. If you read what TI say about the TLE2426 you'll possibly agree: -
In signal-conditioning applications utilizing a single power source, a reference voltage equal to one-half the supply voltage is required for termination of all analog signal grounds. Texas Instruments presents a precision virtual ground whose output voltage is always equal to one-half the input voltage, the TLE2426 “rail splitter.”
You have two power sources namely +5V and -5V and these are likely to have a third wire which you have available that does exactly what the TI chip sets out to do.
Why did the INA129 become unbalanced: -
Using a resistor divider to feed the REF input means that you are altering the 40k resistance at pin 5 and this will unbalance the ratios of resistors and lead to common-mode signal problems.
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Best Answer
You should have no issues running multiple amplifiers from the same virtual ground. However, the virtual ground circuit itself will depend on what your circuit is doing. If you will be driving DC levels, you can't use a simple voltage divider without any buffering, for example. This is a good page that gives an overview of virtual ground techniques:
http://tangentsoft.net/elec/vgrounds.html