Often students of B.Tech often approach me with questions related to constant current source. I suspect that there are many more who choose to keep their question with themselves. So I decided to write this small piece.
So where can I buy a Constant Current Source?
The answer is that unlike cells and batteries, which are constant voltage sources, you can't buy a constant current source (CCS) off-the-shelf (however one can easily build one, more about that later).
A constant current source makes repeated appearances in the life of a serious electronics engineer. So it is useful to understand what it means. Let us use an analogy to do so.
So where can I buy a Constant Current Source?
The answer is that unlike cells and batteries, which are constant voltage sources, you can't buy a constant current source (CCS) off-the-shelf (however one can easily build one, more about that later).
A constant current source makes repeated appearances in the life of a serious electronics engineer. So it is useful to understand what it means. Let us use an analogy to do so.
The analogy in question compares water flow to current flow.
Consider an overhead water tank connected to a solo water tap at ground level. In this case
Consider an overhead water tank connected to a solo water tap at ground level. In this case
1. the height of overhead water tank is analogous to voltage.
2. higher the water tank, more is the potential energy stored in water. This is analogous to a cell of a higher voltage.
2. higher the water tank, more is the potential energy stored in water. This is analogous to a cell of a higher voltage.
3. the water flow in the pipe is then analogous to the flow of electrical energy in the wires.
4. the friction between water and the pipe is analogous to electrical resistance.
With this analogy a constant voltage source is like an overhead water tank of fixed height. A constant current source, on the other hand, is like an overhead water tank of variable height. A constant current source adjusts its output voltage to ensure that the current remains constant.
Now consider the case of an ideal current which is not connected to a load (that is load resistance is infinite and therefore the load current is zero). The current source in this case desperately tries to push its rated current through this open circuit. Thus its output voltage tends to become infinite. In practice it will tend towards the power supply voltage from where this CCS is getting powered. In our analogy, it is like the water tank raising its height in order to push water through a completely closed tap (in our analogous world this is possible).
Comments/questions?
No comments:
Post a Comment