# Voltage Regulator/ Voltage Reference

G

#### GraemeC

Jan 1, 1970
0
Im trying to create a +/- 2.5V supply from a +/-5V. I have a couple
of 2.5V voltage references. Am I right in assuming that I need to get
hold of a -2.5V reference? I did read an article that showed how I
could use an inverter but I don't have any of those either.

There seems to be a gap in my knowledge because I don't really
understand the difference between a voltage reference and a voltage
regulator.

Thanks

G

J

#### John Popelish

Jan 1, 1970
0
GraemeC said:
Im trying to create a +/- 2.5V supply from a +/-5V. I have a couple
of 2.5V voltage references. Am I right in assuming that I need to get
hold of a -2.5V reference? I did read an article that showed how I
could use an inverter but I don't have any of those either.

There seems to be a gap in my knowledge because I don't really
understand the difference between a voltage reference and a voltage
regulator.

If your 2.5 volt references are shunt type (two terminals
that hold 2.5 volts when an externally limited current is
passed through), you can use two of them to regulate a small
(milliamperes) supply. If you want a more significant
current from these supplies, you should use actual supply
regulators. The adjustable LM317 and LM337 pair can be set
to 2.5 volts output with a pair of resistors.
http://www.fairchildsemi.com/ds/LM/LM317.pdf
http://www.fairchildsemi.com/ds/LM/LM337.pdf

J

#### Jonathan Kirwan

Jan 1, 1970
0
Im trying to create a +/- 2.5V supply from a +/-5V. I have a couple
of 2.5V voltage references. Am I right in assuming that I need to get
hold of a -2.5V reference? I did read an article that showed how I
could use an inverter but I don't have any of those either.

You need a low-impedance driver set at 2.5V relative to your current
ground and this new low impedance driver needs to source or sink
(two-quadrant, if my hobbyist knowledge of terms is close to right.)

You don't say what your _current_ requirements will be. There's a
simple answer if you are talking about a few tens of mA. This is the
TLE2426 "rail splitter." Also, an opamp set up with the 2.5V
reference to its (+) input and its (-) tied to its output, which
drives the new center point "ground" might be okay, assuming your
opamp can deliver the current requirements you are looking for. (Or
just use a resistor divider instead of the 2.5V reference, to the (-)
input.) A discrete splitter could be formed out of transistors, too.
There seems to be a gap in my knowledge because I don't really
understand the difference between a voltage reference and a voltage
regulator.

A reference usually has a very small _current_ drive capability -- not
uncommonly in microamps -- to name one important difference.

Jon

J

#### Jonathan Kirwan

Jan 1, 1970
0
(Or
just use a resistor divider instead of the 2.5V reference, to the (-)
input.) A discrete splitter could be formed out of transistors, too.

Sorry, I meant (+), not (-).

Jon

J

#### Jamie

Jan 1, 1970
0
GraemeC said:
Im trying to create a +/- 2.5V supply from a +/-5V. I have a couple
of 2.5V voltage references. Am I right in assuming that I need to get
hold of a -2.5V reference? I did read an article that showed how I
could use an inverter but I don't have any of those either.

There seems to be a gap in my knowledge because I don't really
understand the difference between a voltage reference and a voltage
regulator.

Thanks

G
use a 2425 and turn it around.
the COM will be the - line and (IN) your common .