Re: what makes this oscilator oscilate
Thanks but I dont know what is the charge path.
When we power on the circuit, it stablish the Vbe potential. For Q1 it will be:
Vbe1 =Vcc - I R3 and for Q2 Vbe2 = Vcc - I R2
So, if we take a look at C1
one potential will be Vbe2 and the other Vce1
So, the voltage across C1 will be
Vc1 = Vbe2 - Vce1
And for almost all transistor Vce(sat) is less than Vbe
vc1(t) = 1/C * ∫ ic1(t) dt
(Vcc - 0.7= = i(t) R2+ 1/C * ∫ ic1(t) dt
ic1(t)= (Vcc-0.7) * exp (-t / R2 C1)
and
ic2(t)= (Vcc-0.7) * exp (-t / R3 C2)
When the capacitor is completed charge, ib for will increase (lets say that the C1 charge first)
ib2= (Vcc - 0.7)/R2
where the diference was
Δ ib = (Vcc - 0.7)/R2 - ic1(t)
and as ib2 increase, so Ic2 will increase
Ic2 = β ib2
and Vce2 will decrease because on R4 the voltage will be bigger. and then?
So. What is the charge path?