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How does the pull up resistor work on a VCC?
When the button is pressed, the input pin is pulled low. The value of resistor R1 controls how much current you want to flow from VCC, through the button, and then to ground. When the button is not pressed, the input pin is pulled high. The value of the pull-up resistor controls the voltage on the input pin.
What causes current to flow from collector to emitter?
If the voltage at the cathode is higher than the base, this flow of current through the base-emitter junction will cause current to flow from collector to emitter. However in your case, the collector is not at a higher potential than the base, it is at a lower potential.
How is the collector connected to the supply voltage?
The Collector is connected to the supply voltage VCC via the load resistor, RL which also acts to limit the maximum current flowing through the device. The Base supply voltage VB is connected to the Base resistor RB, which again is used to limit the maximum Base current.
Do you need an IC pin for a MCU?
Outputs normally do not need them. But most mcu pins are GPIO, and sometimes on startup are defined as inputs instead of outputs. As you said, sometimes you don’t want an IC pin input floating on startup, especially like a reset pin that you would normally drive with your microcontroller’s GPIO.
Why do Mpu use pullup / pulldown resistors?
This pattern has several uses including allowing any one MPU to signal an error or turn an LED on, or allowing them all to take turns sending messages to each other on a single wire. As you stated, using pullup/pulldown resistors on pins expected to be output pins can be there to guarantee an input state.
What should the impedance of a pull up resistor be?
The general rule for condition 2 is to use a pull-up resistor (R1) that is an order of magnitude (1/10th) less than the input impedance (R2) of the input pin. An input pin on a microcontroller has an impedance that can vary from 100k-1MΩ.
https://www.youtube.com/watch?v=hPElOK3HLiM