Engineering What is the output of this UJT relaxation oscillator circuit?

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The discussion revolves around analyzing a UJT relaxation oscillator circuit, with participants attempting to determine the output without specific voltage values like VEB or VBB. It highlights the challenges of working with variable specifications of active devices, suggesting that assumptions may be necessary for calculations. Participants discuss the output signal's shape and frequency, emphasizing the importance of understanding the circuit's components, including the PNP transistor's role. The conversation also touches on the need for clarity in terminology and the formulas used for capacitor charging to derive the frequency of oscillation. Ultimately, the discussion reflects the complexities of circuit analysis and the collaborative effort to solve the problem.
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  • #32
Hmmm... no flowers or anything!

190/100 :rolleyes:
 
  • #33
Femme_physics said:
I assume as in before Vout = Vp + Veb ?
Was this established somewhere before? If you mark "voltage arrows" on your schematic, using KVL, you'll be able to demonstrate whether this should be a + or a minus Veb.

You are deciding here how to sketch the Vout pulse, and you need Vout's maximum value in order to sketch it. We know Vp (from Vcc and the manufacturer's data), so what value are you going to use for VEB in the above equation?
 
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  • #34
NascentOxygen said:
Was this established somewhere before? If you mark "voltage arrows" on your schematic, using KVL, you'll be able to demonstrate whether this should be a + or a minus Veb.

You are deciding here how to sketch the Vout pulse, and you need Vout's maximum value in order to sketch it. We know Vp (from Vcc and the manufacturer's data), so what value are you going to use for VEB in the above equation?

You're right, I confused the signs

http://img825.imageshack.us/img825/336/signsz.jpg
 
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  • #35
Can you check that last line ...
 
  • #36
Oh, sorry

Vout = Vp - Veb
 
  • #37
Confirmation?
 
  • #38
Femme_physics said:
Confirmation?
Ah, that's looking better. :smile:

Though I'm still wondering what value you'll use for that unijunction transistor's VEB?
 
  • #39
We don't know its value so we can't actually solve it, just leave it as an unknown

We can make the assumption it's 0.7 volts of course...but maybe it's best to stay on the safe side and leave it as an unknown?
 
  • #40
Femme_physics said:
We don't know its value so we can't actually solve it, just leave it as an unknown

We can make the assumption it's 0.7 volts of course...
If you need a value, it's going to be the value of VEB when in the breakdown region, viz. VV. For your problem, VV is given as 2.1V (or maybe 1.1V depending on which question is considered).
 
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