Getting a steady supply of current by a steady voltage

[ChrisGreece52]

Hello i know the title is a little bit confusing but i was just lost myself.

The problem is simple.

Lets say that we have a regulator that provides 5 volts and up to about 800mA when supplied by a 3.6 volt source like a battery.
But when the battery voltage drops lets say to 1.8 volts the current that it will be able to supply drops to about 100mA max.
The ic i am referring to is the TPS61200.
So i would like to get a steady supply of 5 volts and up to 800mA by creating a current amplifier circuit at the output of the ic
 is this even possible ? Let me know please because i am lost ...

[IanB]

If under given conditions the device can produce a maximum of 100 mA at 5 V, and you wish for 800 mA, then you will need eight of the devices in parallel (5 V x 100 mA = 500 mW, 5 V x 800 mA = 4000 mW, 4000 / 500 = 8 ). It goes without saying you probably will also need eight batteries to power the eight devices.

Your best choice is to use a lithium ion battery that is big enough to supply the required current at 3.6 V. You cannot in any case drop a lithium ion battery to 1.8 V. The voltage is not permitted to go that low.

[ChrisGreece52]

Thank you for your answer silly me i did not say i was going to use a Lion battery to begin with so ill have no problem with whats you just said ...
but just in case i shall create a protection circuit to prevent over discharging the battery

[IanB]

It is still much better to supply the boost converter with a voltage of 3.6 V or more. If you let the voltage go lower than that the conversion efficiency will become very poor and you will waste a lot of power.

[mikerj]

Hello i know the title is a little bit confusing but i was just lost myself.

The problem is simple.

Lets say that we have a regulator that provides 5 volts and up to about 800mA when supplied by a 3.6 volt source like a battery.
But when the battery voltage drops lets say to 1.8 volts the current that it will be able to supply drops to about 100mA max.
The ic i am referring to is the TPS61200.
So i would like to get a steady supply of 5 volts and up to 800mA by creating a current amplifier circuit at the output of the ic
 is this even possible ? Let me know please because i am lost ...

It is possible, but you would need a separate supply for your current amplifier so it makes little sense to do this.  You can't have a passive circuit that magically increases the output power of a DC supply.

[ChrisGreece52]

Yeah after i posted the thread i thought about the current amplifier idea and i think its defies the laws of physics for the purpose i need it for.
But what can i do to have a steady 5 v output with a decent amount of current.
I think i would be better of if instead of a step up ic i used a fet amplifier.... or am i wrong ?