Correct Terminology - Page 1
Forum section: electronics / beginners

author: Bryan
author_rank: Frequent Contributor
timestamp: February 04, 2016, 02:57:27 am
content: 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.

author: Rerouter
author_rank: Super Contributor
timestamp: February 04, 2016, 03:01:06 am
content: Biasing, Or Removal of DC Bias otherwise known as capacitive coupling

author: Richard Crowley
author_rank: Super Contributor
timestamp: February 04, 2016, 03:21:55 am
content: 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.

author: Brumby
author_rank: Unknown
timestamp: February 04, 2016, 04:10:32 am
content: Yep. I was thinking of DC offset ... the removal thereof.

author: vk6zgo
author_rank: Super Contributor
timestamp: February 04, 2016, 04:28:55 am
content: Quote from: Bryan on February 04, 2016, 02:57:27 amVmax & Vmin are not used if referring to a sine wave withnodc 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 thedcvoltages 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)

author: Bryan
author_rank: Frequent Contributor
timestamp: February 04, 2016, 07:04:38 am
content: 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.

author: Brumby
author_rank: Unknown
timestamp: February 04, 2016, 11:29:28 am
content: 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.