|
555, 1n4001, that340 (2) matched npn and pnp pairs.
The 1st pot sets the charging current.
The 2nd pot sets the discharging current.
The 2 pnps form a sourcing current mirror that feeds the switching network with a constant current. The 2 npn do the same, except they sink a constant current from the switching network.
Together, they form a precise way to charge and discharge the cap of the 555 in a linear way, making calculations much easier
The diodes act as a switch to control the charge and discharge cycles.
When the potential at the left side is high, the current is sourced to the capacator and sinked from the control signal.
When the potential at the left side is low, the current is sourced to the control signal and sinked from the capacator.
|
