How much current I need from Vdd and Vss of an amplifier to generate 1A of current

Thread Starter

Oussama Zaidi

Joined Mar 1, 2016
53
Hi
I need to generate a DC signal which can have a positive or a negative voltage for example any value from -15V to +15V and can reach 1A of current, I use an amplifier that can provide 1A of current to generate that signal so the amplifier need to be supplied by a positive and negative voltages for example Vdd=+20V and Vss=-20V so my question is how much current I need from the positive and the negative supplies? I use a generator to get the +20V which can give me as much current as I need but for the -20V I am using a switching regulator the probleme is that the regulator can give me only 100mA of current and I don't know now if I need more or just I can seek the current from the generator, I hope the question was clear, thank you.

Alec_t

Joined Sep 17, 2013
11,818
If your regulator is limited to 100mA for thermal reasons then that's all you can draw without letting out the magic smoke. Use a different regulator if you need 1A.

Thread Starter

Oussama Zaidi

Joined Mar 1, 2016
53
If your regulator is limited to 100mA for thermal reasons then that's all you can draw without letting out the magic smoke. Use a different regulator if you need 1A.
So you say that if I want 1A in the output I need 1A from Vdd and 1A from Vss ?

Alec_t

Joined Sep 17, 2013
11,818
You said:
I need to generate a DC signal which can have a positive or a negative voltage for example any value from -15V to +15V and can reach 1A of current
If your signal needs 1A when V is negative then yes, the negative supply must be able to provide 1A.

ErnieM

Joined Apr 24, 2011
8,090
Unless your amp is made of magic fairy dust you will need somewhat more that 1amp as a real worls amp will consume some power all by itself.

How much depends on the amp itself. Either read the spec sheet or do some experiments.

Or just buy a +/- 2 amp supply and be done with it. You'll need that anyway to do the experiment.

Dodgydave

Joined Jun 22, 2012
9,876
You cant do it from a 100mA supply, you will need a supply that will give out 2 amps minimum, so buy a psu or make one.

crutschow

Joined Mar 14, 2008
26,074
The word "amplifier" doesn't mean it makes more current than available from the supplies,
it just means the output voltage/current can be greater than the input (control) voltage/current, but the output current is supplied by the power supply.
So the supply current has to be at least as large as the output current.

Last edited:
Thread Starter

Oussama Zaidi

Joined Mar 1, 2016
53
The word "amplifier" doesn't mean it makes more current than available from the supplies,
it just means the output voltage/current can be greater than the input (control) voltage/current, but the output current is supplied by the power supply.
So the supply current has to be at least as large as the output current.
I know my question was if I can get all the current that I need from Vdd so it doesn't matter how much current I can get from Vss.

ErnieM

Joined Apr 24, 2011
8,090
I know my question was if I can get all the current that I need from Vdd so it doesn't matter how much current I can get from Vss.
It matters unless your load had a diode in series with it.

What is your load?

crutschow

Joined Mar 14, 2008
26,074
I know my question was if I can get all the current that I need from Vdd so it doesn't matter how much current I can get from Vss.
If you want both a positive and negative output voltage then you require current from Vdd for the positive current and Vss for the negative current.