Electronics > Beginners
Basic Circuit Help
(1/1)
Adam60:
Can someone explain the current flow in this circuit to me. When the switch is closed, what happens in this circuit? Why am I seeing 5.5V on the base when my input voltage is only 4.5V? I am confused. Maybe it is because I understand everything in conventional theory and not electron theory? I think I understand it but not 100% sure about the voltage.

EDIT: I just read that the switch that is closed is a variable capacitance switch. I have not measured the value but I am thinking this may have an effect on the voltage? Any thoughts?

 
rstofer:
What's it supposed to be?
Where did it come from?
It looks like a code practice oscillator with adjustable tone.
Electron theory vs conventional current flow has nothing to do with anything beyond the physics level.  Always use conventional current flow!
The switch itself isn't 'variable capacitance', it simply changes the oscillator capacitance (I believe).
It's entirely possible that when the circuit oscillates, the average base voltage rises up somewhat.  I would expect to see an AC signal so if you are measuring DC, you might want to look at AC only on your meter.

james_s:
If it is an AC signal, your meter may be lying to you. Unless it is a true-RMS meter I would expect it to read incorrectly on anything other than a 50-60Hz sine wave. Even if it is true RMS it will have limitations and will only be accurate within a certain frequency range.
6PTsocket:

--- Quote from: james_s on August 22, 2018, 10:52:04 pm ---If it is an AC signal, your meter may be lying to you. Unless it is a true-RMS meter I would expect it to read incorrectly on anything other than a 50-60Hz sine wave. Even if it is true RMS it will have limitations and will only be accurate within a certain frequency range.

--- End quote ---
That depends on the DMM. Some have better AC voltage frequency response than others. My old Tektronics TX3   is pretty flat through the audio frequencies, one of the reasons I bought it. .4% + 2 counts from 40 to 20k.

Sent from my SM-G900V using Tapatalk

james_s:
The Tektronix TX3 is a true-RMS meter, so yes I would expect it to be fairly accurate over a wider range of frequency and waveforms, that's what True-RMS refers to.
Navigation
Message Index
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod