Transistor Floating pin/switching speed

Thread Starter


Joined May 25, 2020
Hey guys, here I have an example of a signal drive with a transistor, but this "circuit" got something that I can't fully understand, can someone explain to me what is the purpose of these "extra"components, and what are the changes they make to the circuit (wave form etc)?
? (Sorry for my bad scheme, I hope you can understand) Thanks Everyone!


Joined Oct 8, 2019
1 - Diode. When MCU output goes low, the diode conducts and turns off the transistor.
2 - 47K. With the 1K at the input, it forms a voltage divider to limit the voltage to the transistor base.
3 - Diode. Any negative spikes on output are shorted to ground to protect the transistor.