# Voltage Level

Discussion in 'General Electronics Chat' started by viju, Feb 27, 2009.

1. ### viju Thread Starter Senior Member

Sep 28, 2008
120
0
Could someone explain me why these Voltage levels come into exist in the field of electronics?

a) 5 Volts
b) 12 Volts
c) 24 Volts

Why and from where these numbers come from?Is there any significance?

Apr 5, 2008
15,806
2,389
Hello,

The voltage are related to either component or battery size.
5 Volts, most digital electronics works on 5 Volts.
12 Volts, the normalized voltage of a car battery.
24 Volts, the normalized voltage of a truck battery. Can deliver more power at the same current.

Greetings,
Bertus

3. ### viju Thread Starter Senior Member

Sep 28, 2008
120
0
Thankyou very much for the reply Mr.Bertus.

Have the car and truck batteries evolved before the evolution of electronics components?

I am not able to find in the internet why only these numbers come.

Apr 5, 2008
15,806
2,389
Hello,

There are much more voltages used.
Inside a PC you will find many other voltages.
+12 Volts, - 12 Volts + 5 Volts + 3.3 Volts and much lower voltages like 1.8 Volts for the memory and 1.2 - 1.5 Volts for the CPU core.
These are related to the power needed.
Take a look at different audio power amplfiers, there you will see many different voltages.

In RF power circuits you will often find 28 Volts as power supply.
Many RF power transistors are made for 28 Volts.

Greetings,
Bertus

5. ### davebee Well-Known Member

Oct 22, 2008
539
46
The TTL logic family with its 5 volt logic level has become very popular, but if you will look at the chart at the bottom of this wikipedia page you can see that there are lots of different voltages in use in logic circuits, both before and after TTL.

http://en.wikipedia.org/wiki/Logic_family

So 5 volts has become a common logic voltage level but really isn't unique.

There are fundamental voltages of around the 1 volt level associated with diode and transistor junctions, based on the physical properties of the elements involved, so combinations of several of these junctions will need several volts to operate, which explains why most logic is around a few volts instead of something like 6 microvolts or 75 kilovolts.

Similarly, the lead-acid battery has a chemically defined voltage of about 2 volts per cell, so any battery made up of these cells will be a multiple of 2. Six volt batteries were common in many cars many years ago, so again, 12 volts is a common value nowadays but isn't unique.

6. ### viju Thread Starter Senior Member

Sep 28, 2008
120
0
Great help.

I could find some theoritical relationship in AC voltages due to form factor (1.11) which inturn gives us 110V,220V, 440V,3.3KV,6.6KV,11KV,22KV,33KV and so on.Put it in a nut shell all voltages are multiples of 1.11.

Just I wanted to know was there any sort of information like this.
Anyways great help.Thankyou members.

7. ### italo New Member

Nov 20, 2005
205
1
I am old enough to remenber 6v battery for cars. why the 12v and 24v anDd12v which for a fully charged battery is realy 13.68v is as explained before because of bigger engine and bigger power required to start them. The 5V evolved from manufactures decision the settle for a suitable voltage to be applied to theyr IC.