
477
Because TR! is bottomed, v
cl
is only just above zero. And because
C
x
has had no time to charge, v
b2
is pushed down to the same extent.
Although in doing so it cuts off TR
2
, v
c2
cannot instantly spring up
to + V
cc
, because C
2
has to charge through R
2
and TRj (base to
emitter). So v
c2
rises exponentially as shown. v
bl
is thereby pushed
positive, but only slightly and temporarily because of the charging of
C
2
. When that is complete v
bl
is held at a small positive bias by
current via R
4
. This fall-off in v
bl
reduces the TRj collector current
slightly, so there is a slight rise in v
cl
. Meanwhile C
b
held on the left
at the near-zero v
cl
, is chargin ...