Whats it called when a waveform starts BELOW the zero crossing point?
example: triangle waveform
starts from -6 goes up to +4
or starts -10 goes up to +2
Mostly DC offset Raises the Waveform up ABOVE the zero crossing point what makes the waveform go Below the zero crossing point? what would cause the circuit to do this?
Superimposed is taking a DC voltage and having AC waveforms riding on top
making the AC waveform go "Above the Zero crossing point
Is there anything else like a network or circuit that would make the AC waveform go 'Above" or "Below the zero crossing point?
Suppose two terminals A and B and B is the referance point (gnd/0v) now if A is more positive than B we say its +1V and if it is lees than B we say its -1V
the flow of the current will also reverse according to this.
superimposing a +ve voltage will make a waveform go up above zero , likewise a -ve voltage superimposing will drag it down below Zero .
Think of Zero/Ground only as a common reference point only..
take a very small time slice of a waveform that starts at -6v ok..
now as earlier consider two terminals A nd B with B as reference(0v) . now -6v at a moment means the Termonal A have 6v 'lower' potential than B , and we donote it by - . it doesn't mean that it has a -ve power supply.
but how do i start the wave at -6 or -12 thats my problem is what makes the waveform start at -4 or -6 ,-8,-12 how do i get the waveform below the zero voltage do i use a negative power supply or what circut does this?
but how do i start the wave at -6 or -12 thats my problem is what makes the waveform start at -4 or -6 ,-8,-12 how do i get the waveform below the zero voltage do i use a negative power supply or what circut does this?
have u understood the 'reference point' concept clearly?
u don't require a '-ve' power supply for this .
if a waveform oscillates above the '0' (means it has static dc component) . just pass the wave thru a capacitor . u will get a bipolar wave.
logically speaking, anything below 0 is negative, and anything above 0 is positive.
Seeing that kind of waveform means that your circuit must be starting in the inverted mode. For example, if you had a circuit whichs turns a light on and off, then in the inverted mode, the light will start off, and then turn on. I am making the assumption that the light is connected to 0V.
mstechca, I don't think he was talking about a logic circuit, since his example was a triangle wave...
you can add a DC offset to an AC signal using a simple op-amp circuit (or perhaps an AC-coupling cap and a couple biasing resistors, in some cases) There is no real difference in adding a positive or negative DC offset, it's just in how you set up the circuit. of course, you would need to have a negative supply voltage to run the op-amp.
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