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how to generate a constant voltage source???

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afujian

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How to generate a constant voltage source that can supply different current?Thanks a lot.
 

a 'voltage regulator' is classic example of
constant voltage source.

(or) ,
a battery (within its discharge rating ) is another one.

srizbf
30thapril2010
 

srizbf said:
a 'voltage regulator' is classic example of
constant voltage source.

(or) ,
a battery (within its discharge rating ) is another one.

srizbf
30thapril2010
thanks,but I will not use a battery,my goal is to design such a voltage source,and the voltage regulator may be the suitable one.

Added after 2 minutes:

calculus_cuthbert said:
are you talking about a voltage controlled current source?
nope, it should be an constant voltage source ignoring its current.

Added after 3 minutes:

srhoar said:
For it to be a constant voltage source, it has to be able to supply different currents.

If the load on the driver changes, then the current must change.

Voltage
-------- = current
Load

https://en.wikipedia.org/wiki/Voltage_source

Just put a zener diode across the source.

Red
yes,the voltage regulator.

Added after 6 minutes:

But,what is the difference between the voltage regulator and the bandgap reference? both of them can supply congstant voltage!
 

Voltage regulators are designed to supply a significant current - up to several amps at a constant voltage, a bandgap will provide a more stable voltage than a regulator over temperature, but only up to a few mA. A bandgap is one element of a voltage regulator.

Keith
 

    afujian

    Points: 2
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You need to specify the voltage, current, tolerances, temperature coeficient and everything else you are interested in to get a more specific answer. Please be more specific in your posts.
 

keith1200rs said:
Voltage regulators are designed to supply a significant current - up to several amps at a constant voltage, a bandgap will provide a more stable voltage than a regulator over temperature, but only up to a few mA. A bandgap is one element of a voltage regulator.

Keith
Thanks,your answer is helpful.Please also pay attention to the attachment,is it possible to fix the Vx to a constant value without using a bandgap and voltage regulator(because it is a part of a bandgap circuit) as the vdd changes from 2v to 5v.------I hope have disccribed the question distinctly.
 

It might be useful if you explained more about what you are trying to do. A fixed voltage required as part of a bandgap design? Your circuit will probably produce a voltage a roughly fixed amount below Vdd, but it will change as Vdd changes. Is this a startup circuit for a bandgap? Your requirements are rather vague.

Keith
 

It's a little complicate to explain it.The circuit is assumed to be a part of my bandgap circuit,I want it to generate a current which can be expressed as I=a*T square+b*T+c (T means Temperature) to do a second order curvature compensation.The principle is if the Vx is fixed,and the voltage of Vbias equals -kT+b,then according to the equation Id=1/2*u*cox*w/l*(vsg-vth)square,the I is generated.Now the only problem is how to fix the Vx to a constant value while the vdd is changing.Finally if this current is injected to the output branch,the compensation may be achieved.
 

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