| Electronics > Beginners |
| converting Volt into dB |
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| mikerj:
--- Quote from: bob91343 on August 07, 2019, 12:26:06 am ---Strictly speaking, dB has to be power gain. Output power divided by input power gives the power gain ratio. Take the logarithm of that (base 10) and multiply by ten to get the result in dB. --- End quote --- I don't understand this, dB is simply a log scale, it can be used with many different units. Are you saying that using it for e.g. electric field strength or bandwidth is wrong? |
| radiolistener:
you can use it for different units. For example there is popular unit dBuV (decibel micro-Volt) |
| Audioguru again:
The inverted output of the transistor has no load so its voltage gain is 20 times which is +26dB. It has some output impedance so its output level and voltage gain will drop when it has a load. Then you can calculate its power gain if you want. edit: Because it inverts, its output phase is negative, not its gain. |
| pepelevamp:
ya know i figure you don't need to be talking about power or what not to use decibels. its simply a way to talk about scales easily. but the power db versus voltage db - that can be confusing. |
| bob91343:
I reiterate that decibels are a measure of power ratio. Any other use is perversion. Having said that, it's popular culture to use decibels for other purposes, although it's clearly wrong. As for using it for field strength, etc., it's still a valid power ratio. We don't say that a 2 Ohm resistor is 6 dB higher than a 1 Ohm resistor. Decibels are properly used for power ratio. Saying an amplifier has such and such decibel gain is improper. But common practice. The bottom line is that you can be precise or not but if your audience understands your meaning you can get away with however you say it. |
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