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

#### 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
14,312
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.

#### 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
14,312
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
8,377
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
11,300
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
34,390
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.

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#### 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
8,377
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.