Author Topic: Correct Terminology  (Read 1567 times)

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Offline Bryan

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Correct Terminology
« on: February 04, 2016, 02:57:27 am »
Hello:

What is the correct terminology and technique if you want to modify the Vmax and Vmin of a sine wave so they are equal. I keep thinking level shifting but that is not it. I know some refer to Vmax as Vpp, but I am referring to the voltage above and below the ground baseline.
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Offline Rerouter

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Re: Correct Terminology
« Reply #1 on: February 04, 2016, 03:01:06 am »
Biasing, Or Removal of DC Bias otherwise known as capacitive coupling
 

Online Richard Crowley

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Re: Correct Terminology
« Reply #2 on: February 04, 2016, 03:21:55 am »
Perhaps "offset" (DC bias) is the word you seek?

People who edit and analyze Real World audio waveforms (speech, music, natural and artifical sounds) have come to observe that a surprising amount of audio is quite non-symmetrical. For example with much more power above the zero than below it (or vice-versa).  And NO, I am not talking about DC offset or bias.  It is a semi-FAQ in many audio production forums.
 

Online Brumby

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Re: Correct Terminology
« Reply #3 on: February 04, 2016, 04:10:32 am »
Yep.  I was thinking of DC offset ... the removal thereof.
 

Online vk6zgo

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Re: Correct Terminology
« Reply #4 on: February 04, 2016, 04:28:55 am »
Hello:

What is the correct terminology and technique if you want to modify the Vmax and Vmin of a sine wave so they are equal. I keep thinking level shifting but that is not it. I know some refer to Vmax as Vpp, but I am referring to the voltage above and below the ground baseline.

Vmax & Vmin are not used if referring to a sine wave with no dc offset.
A moments thought shows that both the positive & negative peaks are "max",& the only "min" is the zero crossing.

The only time they are correct usage is when there is a dc offset of the signal as below:

(1)Vmin & Vmax:-
Amplifier devices & ADDs are normally dc coupled internally,so the input signal will have a dc offset .
If it is a positive offset,the sinewave  positive half cycle will add to the dc voltage,& the negative half cycle will subtract from it.
The inverse will be the case for a negative offset.

The effect upon the dc voltage will thus be maximum at the sine wave peaks,so the dc voltages resulting become Vmax & Vmin

(2)Vpp:-

Vpp is normally used in two situations:
(a)As a convenient way of measuring ac waveforms on Oscilloscopes.
Obviously,the positive & negative half cycles are not present at the same time.

(b)A device,such as an amplifier,or a ADD must be able to handle the whole dynamic range of the sine wave,from peak negative to peak positive without distortion,hence Vpp is a useful  parameter,used in conjunction with Vmax & Vmin as in (1)
« Last Edit: February 04, 2016, 04:32:18 am by vk6zgo »
 

Offline Bryan

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Re: Correct Terminology
« Reply #5 on: February 04, 2016, 07:04:38 am »
Thank you everyone, that is exactly the explanation I was looking for. So in short AC coupling rejects the DC component of the signal. Effectively, this normalizes the signal to a zero mean. I added a 1nf cap to the circuit and sure enough the signal normalized. However is there a calculation for the capacitor value for a specific frequency and or voltage. I have a signal from a  rubidium output that I want to clean up before sending it to a distribution amplifier. The frequency is 10Mhz and around 3.2v Vpp.
-=Bryan=-
 

Online Brumby

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Re: Correct Terminology
« Reply #6 on: February 04, 2016, 11:29:28 am »
The capacitance is not going to be too critical - it will just act as a high pass filter for AC signals.  The bigger the value, the lower the roll-off frequency, but for a specific frequency things are a lot easier.  For 10 MHz, you wouldn't need anything above 0.01uF.
 


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