A Regulated Virtual Ground and Rail Splitter
This circuit enables a DC power supply or wall adapter with a two conductor output to function as a split supply with a three conductor output (i.e., positive, negative AND ground). And because it is capable of drawing only a few milliamps of quiescent current (as low as 3 - 5mA), it is also suitable for use with portable gear running from a single battery, such as a 6V, 9V, or 12V, or any battery voltage from about 5V to 40V.
Capabilities: 1.5 Amps continuous on each positive and negative output, @ about +/- 37V.
![Click the image to open in full size.]()
How it works: The two voltage regulators, one positive, the other negative, operate in parallel, their opposite polarity outputs tied together through small resistors - creating a "rock solid" virtual ground. The LM336-2.5 voltage reference (2.5V) compensates for the LM317's 1.25V internal reference and the LM337's -1.25V internal reference. So compensated, each voltage regulator outputs 1/2 of whatever the the rail-to-rail voltage happens to be. This sort of "self centering" circuit is also called a "rail splitter".
If powered from a 9V battery, the circuit will continue to work with the battery drained down to about half.An LM336-2.5 can operate with as little as about 0.5mA, although typically rated for up to 10mA of forward current.. The LM317/LM337s will continue to regulate with an Input voltage as low as 3.7 volts. Minimized for portable gear:
![Click the image to open in full size.]()
For battery operation you can set R1, R2 to draw an absolute minimum amount of quiescent current (about 1.5mA). This may result in a ground point offset (not being perfectly centered between the +/- rails) of about 0.15V, (which may not be significant in actual use). But if using an AC powered power supply, set R1, R2 for higher current (about 8mA), which should typically result in a perfectly centered ground point (0.00V offset).
Unlike the famous TLE2426 rail splitter which can sink or source 20mA, this rail splitter can handle 1500mA (that's 1.5 amps) of constant current on both the positive and the negative outputs simultaneously. And if your load draws less than about 75mA, you should not need any heat sinks on the two TO-220 size regulators.
Although a simple and inexpensive virtual ground solution, some audio designs may actually sound better when using this regulated ground. For example, this could mean better sounding bass when driving 32 ohm (or lower) loads. I suspect that the reason for it's unusually good sound quality is that "it holds the ground point firmly in place with voltage regulators", instead of merely driving a ground point with some form of Class AB or Class B amplifier (after being demanded to), the way many other virtual ground circuits go about it. (Let us know your sonic results!)
Original posting with additional data at: http://www.goldpt.com/virtual_ground.html
Capabilities: 1.5 Amps continuous on each positive and negative output, @ about +/- 37V.
How it works: The two voltage regulators, one positive, the other negative, operate in parallel, their opposite polarity outputs tied together through small resistors - creating a "rock solid" virtual ground. The LM336-2.5 voltage reference (2.5V) compensates for the LM317's 1.25V internal reference and the LM337's -1.25V internal reference. So compensated, each voltage regulator outputs 1/2 of whatever the the rail-to-rail voltage happens to be. This sort of "self centering" circuit is also called a "rail splitter".
If powered from a 9V battery, the circuit will continue to work with the battery drained down to about half.An LM336-2.5 can operate with as little as about 0.5mA, although typically rated for up to 10mA of forward current.. The LM317/LM337s will continue to regulate with an Input voltage as low as 3.7 volts. Minimized for portable gear:
For battery operation you can set R1, R2 to draw an absolute minimum amount of quiescent current (about 1.5mA). This may result in a ground point offset (not being perfectly centered between the +/- rails) of about 0.15V, (which may not be significant in actual use). But if using an AC powered power supply, set R1, R2 for higher current (about 8mA), which should typically result in a perfectly centered ground point (0.00V offset).
Unlike the famous TLE2426 rail splitter which can sink or source 20mA, this rail splitter can handle 1500mA (that's 1.5 amps) of constant current on both the positive and the negative outputs simultaneously. And if your load draws less than about 75mA, you should not need any heat sinks on the two TO-220 size regulators.
Although a simple and inexpensive virtual ground solution, some audio designs may actually sound better when using this regulated ground. For example, this could mean better sounding bass when driving 32 ohm (or lower) loads. I suspect that the reason for it's unusually good sound quality is that "it holds the ground point firmly in place with voltage regulators", instead of merely driving a ground point with some form of Class AB or Class B amplifier (after being demanded to), the way many other virtual ground circuits go about it. (Let us know your sonic results!)
Original posting with additional data at: http://www.goldpt.com/virtual_ground.html