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I apologize if this question has been asked already, but after some frustrating Google searches I'm really tired of finding the same answers that I don't understand and decided to ask the question specifically regarding my issue. I found an amplifier circuit that looks ok and to which I actually managed to scrape up all the parts for, but there is an open end labeled "-vcc", which on the board layout they also provided, has an actual thru hole pad, and I'm wondering what I'm supposed to connect there physically to that pad? There is also ground pads.....so do I connect the gnd wire of my power supply to the -vcc or to ground? If ground, what goes to -vcc.? Thank you very much for your time. I'm sorry if I sound like a total noob here.

A voltage is always a difference of electrical tension between two points in space, like a time laps is always the difference between two instants (two date and time instants).

If the tension is higher at point A than at point B, then V_ab = V_a - V_b is positive and V_ba = V_b - V_a is negative.

A ground is a REFERENCE for a SPECIFIC usage of a circuit, so we can use a shortcut of speech by saying "the voltage AT point X", which, in the long form, would be "the difference of tension between point X and the GROUND".

So, for a voltage which is negative AT some point, that means that the electrical tension at the point is smaller than the tension at the (presumed) ground.

A circuit may require a voltage swing, like for an AC signal. The notation is not universal, some companies speak of Vcc and Vee (for the most positive and the most negative allowed voltage), others will speak of Vcc+ and Vcc-, but that always involves a REFERENCE to the assumed GROUND.

Like a maximum speed can be forward or backward, if the orientation matter, one of this speed will be positive and the other negative, it seems that your circuit makes such difference too in what it is doing, which I have no idea of what it is exactly, but need two references, in addition to be at rest, immobile if I continue the speed analogy, or to be at the ground, in electronic (at rest as far as the circuit is concerned).

In the case when a voltage source has negative voltage, it just means the negative terminal of the battery is connected to the positive side of the circuit and the positive terminal of the battery is connected to the negative side of the circuit . Both voltage sources are connected to an LED. https://www.circuitlab.com/questions Flappy Bird

Yes and no. Mainly no. If you reverse the polarity of the battery, you "mirror" the circuit, with a flip along the horizontal of the circuit diagram. In that case, it would add confusion for nothing to speak of "negative voltage".

Strictly speaking a negative voltage at a point is about the electrical tension at this point being less than the electrical tension at the defined "ground". That definition works and for DC and for AC.

That definition works also for "negative pump" which can create negative voltage with capacitor and a clock signal, without "reversing" the polarity of the DC source.

When a voltage source has negative voltage, it simply indicates the battery's negative terminal. geometry dash scratch