suggestion needed............

[miguelbelano]

hi, i'm new in electronics but i have a project that i think would need some electronic genius. given a simple question: how can i make an electronic device that would be able to increase its output current dependent with time? the project would consist of a simple switch and the device that would increase the output current while the switch is kept on, the longer the switch is kept on the more output current is produced. is it possible? to make a device like this? i need your ideas pls........

 

[Papabravo]

A BJT or a FET will do this up to some limit. This limit is determined by the load in the output circuit and the external power supply. There are ways of constructing the input to get different types of output functions.

 

[miguelbelano]

more

thank you for the suggestion papabravo, can you please elaborate further, or any more suggestions?

 

[Brevor]

thank you for the suggestion papabravo, can you please elaborate further, or any more suggestions?

You need to elaborate further before any more advice can be given, such as what is the maximum current that will be required and what will be the source of power.

 

[Papabravo]

thank you for the suggestion papabravo, can you please elaborate further, or any more suggestions?

OK
Connect the switch to one input of an opamp integrator. The integral of a step function is a ramp. Apply the ramp to the gate of FET in the common source configuration. The output current will be a parabolic function of the input voltage above Vgs(th).

 

[mneary]

But if you connect the integrator to a perfect current source then it will be linear. If the opamp integrator has an infinite supply voltage then the output will increase indefinitely. (This will work perfectly but it'll cost an infinite amount of money).

Or you could tell us what you actually want to do.

 

[miguelbelano]

ok, assuming i already have a device that would be the current source, with main switch as well to control the main output. the problem arise from here, after the current from the main, i want to put another switch(which i think i can make) and a device that would increase the intensity output proportionately dependent in time the switch is turned on.