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Guest
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 Posted:
Sat Feb 12, 2005 12:40 am Post subject:
7.26Volts output |
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Hello,
I am new to electronics and I have a project to interface an active
electrode that need a clean 7.26V (+- 0.02V) supply voltage. I would
like to use a 9V battery. The active electrode comsumes 0.7mA. Can I
simply use a series of resistors or do I need a voltage regulator or a
converter?
Thanks
Daniel Jeffrey
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martin griffith
Guest
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| Posted:
Sat Feb 12, 2005 1:12 am Post subject:
Re: 7.26Volts output |
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On 11 Feb 2005 10:40:50 -0800, in sci.electronics.design
danielj@hralloy.com wrote:
| Quote: | Hello,
I am new to electronics and I have a project to interface an active
electrode that need a clean 7.26V (+- 0.02V) supply voltage. I would
like to use a 9V battery. The active electrode comsumes 0.7mA. Can I
simply use a series of resistors or do I need a voltage regulator or a
converter?
Thanks
Daniel Jeffrey
9V is a "nominal" voltage, if it is a rechargeable battery it could be |
as low as 8.4V.
have a look at
http://focus.ti.com/lit/ds/symlink/tl431a.pdf
this is a shunt regulator, which might suit you. Note that it needs a
minimum load, so you would have to put another resistor in paralle
with your electrode, to keep the total current above 1mA. Basic Ohms
law.
You could also look at low dropout regulators (LDO's) from say Ti.com
or national.com
martin
"Facts are stupid things.." -- Reagan, '88 |
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Spehro Pefhany
Guest
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| Posted:
Sat Feb 12, 2005 1:32 am Post subject:
Re: 7.26Volts output |
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On Fri, 11 Feb 2005 20:12:10 +0100, the renowned martin griffith
<martingriffithX@Xyahoo.co.uk> wrote:
| Quote: | On 11 Feb 2005 10:40:50 -0800, in sci.electronics.design
danielj@hralloy.com wrote:
Hello,
I am new to electronics and I have a project to interface an active
electrode that need a clean 7.26V (+- 0.02V) supply voltage. I would
like to use a 9V battery. The active electrode comsumes 0.7mA. Can I
simply use a series of resistors or do I need a voltage regulator or a
converter?
Thanks
Daniel Jeffrey
9V is a "nominal" voltage, if it is a rechargeable battery it could be
as low as 8.4V.
have a look at
http://focus.ti.com/lit/ds/symlink/tl431a.pdf
this is a shunt regulator, which might suit you. Note that it needs a
minimum load, so you would have to put another resistor in paralle
with your electrode, to keep the total current above 1mA. Basic Ohms
law.
You could also look at low dropout regulators (LDO's) from say Ti.com
or national.com
martin
|
Eg. LP2952 -- adjustable LDO (<100mV) with reverse battery
protection-- should draw in the low hundreds of uA. It would need
triming to get within 0.3%. Noise can be quite high with this kind of
part though- hundreds of uV in some cases.
Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
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qrk
Guest
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| Posted:
Sat Feb 12, 2005 6:11 am Post subject:
Re: 7.26Volts output |
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danielj@hralloy.com wrote:
| Quote: | Hello,
I am new to electronics and I have a project to interface an active
electrode that need a clean 7.26V (+- 0.02V) supply voltage. I would
like to use a 9V battery. The active electrode comsumes 0.7mA. Can I
simply use a series of resistors or do I need a voltage regulator or
a
converter?
Thanks
Daniel Jeffrey
|
You could use a precision reference and an op-amp to scale the output
voltage. Your current requirement is well within the output current
capabilities of an op-amp.
There are numerous adjustable low-dropout voltage regulators which
would do the job.
Mark |
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