VCE Stuff > VCE Physics
VCE Physics Question Thread!
Alwin:
--- Quote from: [paradox]+ on April 25, 2013, 04:41:12 pm ---Jasper has a transistor radio with flat batteries. Suggest a reason to explain why the sound is distorted when he tunes in to a strong radio signal.
^help anyone? thanks in advance
--- End quote ---
For this one, I decided to add an image! just because.. I can haha
--- Quote ---The input signal may be too large, causing the amplifier to be limited by the supply voltage.
--- End quote ---
This is true in the case of Jasper and his poor flat batteries. The DC power supply is the two parallel lines, where the voltage supplied is +Vcc and grounded at 0V. I won't go into the specifics of the transistor, since it is no longer on the study design, but simply the "in" signal is the current that enters the middle of the transistor and allows the larger current to flow through (top to bottom) from the DC power source.
Hence, if the DC source is not large enough then it cannont properly amplify the "in" signal because it cannot amplify a strong signal, ie it cannot amplify the strong +ve and strong -ve signals, ie smaller clipping range
Hope that makes sense!
Robert123:
What does a negative gain amplifier actually achieve?
I know it inverts the Vout graph but how does that have a meaningful purpose? What would be the difference in a microphone that is hooked up to an amplifier with a negative gain rather than a positive one?
Thanks :)
Alwin:
--- Quote from: Robert123 on April 27, 2013, 03:04:38 pm ---What does a negative gain amplifier actually achieve?
I know it inverts the Vout graph but how does that have a meaningful purpose? What would be the difference in a microphone that is hooked up to an amplifier with a negative gain rather than a positive one?
Thanks :)
--- End quote ---
There actually is no "purpose" for wanting negative gain. It is just a side effect of using a simple single transistor amplifier, the npn transistor inverts the input signal. If you want a non-inverting amplifier, you need a two-stage amplifier (two transistors). That's the only reason why a lot of amplifiers in physics questions have negative gain since we deal with simple amplifiers.
As for the difference, well there is none. Remember when a microphone or speaker works, it is a diaphragm that vibrates back and forth creating a sound wave. If the initial current is positive, then the diaphragm moves forward, then back, then forward etc. But, if the signal had been inverted, initially the current flows in the other direction and so the diaphragm moves back first then forwards then back again if you get what I mean. So, the frequency of sound produced / recorded it the exact same.
Hope that clears things up for you!
Robert123:
Thank you for that, clears things up a lot :)
Homer:
Hey guys how would you calculate the value of R?
Thanks ;D
ANS: 309.1ohms
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version