# No BJT multivibrator circuits?

Discussion in 'Feedback and Suggestions' started by Vienticus Prime, Jul 13, 2011.

1. ### Vienticus Prime Thread Starter New Member

Jul 13, 2011
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Am I not seeing it or is it simply not there?

I find these are good circuits to talk about to assist in the understanding of transistor circuitry and always try to squeeze a little tidbit about them in my classes.

Mar 24, 2008
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3. ### Vienticus Prime Thread Starter New Member

Jul 13, 2011
2
0
Except for I question the math involved on that page. For example: I don't see how (.6-5)/(.6-2*5) simplifies to 1/2.

4. ### debjit625 Well-Known Member

Apr 17, 2010
790
186

The wikipedia's equation is like this...

Solving for t in:

t = -RC * ln { (VBE_Q1 - VCC)/(VBE_Q1 - 2 * VCC) }

For this circuit to work VCC >> VBE_Q1 .Now the symbol ">>" means "is much greater than" i.e.. the equation is assuming that VBE_Q1 is a very small quantity compared to VCC and subtracting VBE_Q1 from VCC would not make much difference in the value of VCC ,so we are just eliminating VBE_Q1 from the equation and we get

t = -RC * ln { -VCC/-(2 * VCC) }
t = -RC * ln { VCC/2 * VCC}
t = -RC * ln (1/2)

Its like this if x = 0.1 and y = 100,we can say (y - x) is approx y.In figures 99.9 is almost 100.

Good Luck