square wave generator circuit

When the turtle source was first connected. Since the bases of the two transistors are connected to the power supply vo through base resistors
, both tubes have a tendency to conduct electricity. However, the currents in the two tubes cannot be completely equal. This is because the tube characteristics are not symmetrical
(4 grid), and the parasitic capacitance is not exactly the same. There is always one tube with stronger conductivity, such as VT1. Then the collector current
Ja of VT1 increases, and the collector voltage Ud of VT1
will decrease. Since the voltage across the capacitor cl
cannot mutate,
all changes in the collector voltage of VT1 are added to the base of VT2,
making the base potential of VT2 Uh2 decreases, thus
reducing the current of VT2. The decrease of VT2 substrate current
leads to
the decrease of VT2 collector current Id and the increase of collector voltage Ud.
This voltage change, through the coupling of C2,
is all added to VT1. On the base,
the base current Ibl of VT1 increases, so that the collector current
of VT1 becomes larger and larger, forming a positive feedback process.