How does the NPN transistor in a 555 timer discharge the capacitor when the output is low?

Question

I am new to electronics and I'm trying to understand how the 555 timer works based on the diagram below. I am following the tutorial/explanation at https://www.electronics-tutorials.ws/waveforms/555_timer.html

In the tutorial, for the description of pin 7 (discharge), it says:

The discharge pin is connected directly to the Collector of an internal NPN transistor which is used to “discharge” the timing capacitor to ground when the output at pin 3 switches “LOW”

However, I don't understand how the base of the transistor could be allowing the capacitor a path to ground (which would require the base to be "high", if I understand correctly) if the output at pin 3 is "low" at the same time, since they are both connected to /Q. Shouldn't they both be "high" or both be "low"?

Answer 1

"OUTPUT DRIVER" in your diagram doesn't show its logical function (which is a logical inversion). Some other internal diagrams of a 555 shown below.
These diagrams are simplifications. There actually is a transistor connected to pin 7, but its base drive is not shown properly in these diagrams. This transistor is configured as a switch, which is either non-conducting, or it is "ON", pulling a lot of current from pin 7 to ground (pin 1).

Answer 2

I have previously done an LT-Spice simulation of the equivalent circuit of the 555 chip using 2N2904 and 2N3906 transistor models. (Yes you could even physically build a discrete version of the 555 if you detest the IC in its 8-pin package).

Here is a waveform from the simulation showing the OUT, DIS and BASE of the DISCHARGE NPN transistor. Note that the BASE is high during the time the OUT pin is low.

Here is a picture of the simulation schematic. This first part is the connection setup for the 555 model.

Next I show the schematic portion that is the actual 555 model.

If you look closely at the output section (which I show a snip of below) you will note that both the Q14 DISCHARGE transistor and the Q24 transistor that pulls the OUT low derive their base drive from the same source.