Discussion in 'General Electronics Chat' started by sharanbr, Jun 19, 2015.

1. sharanbr Thread Starter Active Member

Apr 13, 2009
76
1
Hello All,

Technically, what exactly is a load on a voltage source?
Is it effective resistance on a circuit on a voltage source?

Also, for a given voltage source, are there limits on how much load can be put on the voltage source?

2. #12 Expert

Nov 30, 2010
16,705
7,358
The load is the sum of all things which allow current to flow from or to the point declared as the voltage source. This can get pretty strange as it include anything from a resistor to a radio frequency antenna to a whole computer board.

Second question: yes. Nobody has yet invented an infinite current source.

3. GopherT AAC Fanatic!

Nov 23, 2012
6,330
4,078
To give an example of #12's lat comment, if the resistance if the load is too small, current will be extremely high and damage the devices that are regulating the voltage.

On the other extreme, some voltage regulators do require a minimum load, 10 mA for an LM317 regulator. Without that 10 mA flowing, compliance to the stated voltage is poor and gets better as the load is increased (as resistance becomes smaller).

Also, I don't think voltage source is a very good term. You should use voltage regulator. Current Source is another way to control a power to a load. In that case, source makes more sense than current regulator. Kind of an analogy to pressure regulator and flow control.

#12 likes this.
4. sharanbr Thread Starter Active Member

Apr 13, 2009
76
1
Dear Gopher, #12,

Thanks a lot. So, if I had my own circuit, then lower the load it puts on voltage regulator (or supply) better is its efficiency ... because lower the current, lower the power dissipated ... Is this correct?

One would intuitively think that lower the resistance the better design is ...

5. GopherT AAC Fanatic!

Nov 23, 2012
6,330
4,078
The regulator dissipates heat according to the equation, (input voltage - output voltage) x current of load.

The load current is always in series with the regulator's current so, by rules of series circuits, the regulator is passing the same current.

Less current means less power. On a percentage basis, the loss is the same no matter how much current is passed (assuming you do not overload your device.