Voltage Potential

[bonjing]

what is potential voltage and How to determine the poential voltage of amplifier.

 

[duffy]

In this case they probably mean the "maximum peak value" of the voltage.

 

[Hero999]

Assuming no transformer is used it's equal to the supply voltage minus the saturation losses of the output transistors.

 

[bonjing]

as an example, how to determine the potential voltage of power amplifier rated 100 watt in order to calculate the rigt speaker rating for it.

 

[duffy]

They are probably assuming 8Ω speakers and a sine wave with an RMS value. Use ohm's law.

 

[bonjing]

let say, potential voltage for a 100 watt at 4 ohm amplifier.

Erms = sqrt of P*R
= 100*4 sqrt
= 20Vrms

Is these correct?

 

[duffy]

Yes, that looks right.

 

[bonjing]

let say, potential voltage for a 100 watt at 4 ohm amplifier.

Erms = sqrt of P*R
= 100*4 sqrt
= 20Vrms

Is these correct?

 

[duffy]

Yes, rms voltage = square root of (power x resistance), that MAY be what they are looking for.

Problem is that "voltage" and "potential" are used interchangeably, so saying "potential voltage" is like saying "voltage voltage". If they mean PEAK voltage, then it's 28 V.

Is this a homework assignment or what?

 

[bonjing]

So, the potential voltage is 20 volts rms across the load.
for calculating the rigt speaker we need a 20 volts of voltage potential in an amplifier , am i right?

how about if we are going to multiply Erms to 1.414? what does it mean again?

 

[duffy]

Are you talking about the positive rail (supply voltage) of the amplifier? For that you need MORE than 28V. Like Hero999 said, the DC supply minus the saturation drop on the drivers.

 

[bonjing]

of coure when calculating a right speaker we need to find out first the source voltage of amplifier which can deliver a voltage potential, some say that it easier to measure the potential voltage across the load.

so, what is a voltage potential? is it in Vrms or Vpeak?

 

[duffy]

In that case they mean Vrms, 20V. "Voltage potential" by itself is an ambiguous term.

 

[bonjing]

how about, if we measure the voltage potential of amplifier across a resistive load? is there any difference?

 

[duffy]

Yes, but it would be BETTER to measure across a 4Ω resistor for this, and use a sine wave from a frequency generator at the input.

 

[bonjing]

ah, ok thanks for the info.

 

[bonjing]

hello...

is there an illustrative of potential voltage measurement across a resistive load?

 

[duffy]

Do you have a scope? Clip one channel to one side of the resistor. Clip the other channel to the other side. Ground the scope to the amplifier ground. Select "Add". Select "Invert". This will subtract channel 1 from channel 2 and give you the difference in voltage.