Hi guys, can someone explain me the purpose of the resistor R2? Thanks!
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. . . in a potential divider with R1, so that it can be connected directly to a logic level output.This resistor increases the turn-on threshold of the transistor switch.
Thanks, one more question, it can work like a pull down resistor too? To avoid that base start floating?. . . in a potential divider with R1, so that it can be connected directly to a logic level output.
R2 also helps remove any stored charge and helps the transistor turn off more quickly.
It IS a pulldown resistor!Thanks, one more question, it can work like a pull down resistor too? To avoid that base start floating?
As we can see in the nice diagram from Bordodynov, it does NOT influence the thresholds but it improves the rise time at the output when the input goes down. This is because the time constant for discharging the BJTs capacitance is determined by the 47k resistor(s) - single vs. parallel.This resistor increases the turn-on threshold of the transistor switch.
If R1 were absent, then it wouldn’t, but with R1 in circuit R2 sets the switch on threshold.As we can see in the nice diagram from Bordodynov, it does NOT influence the thresholds but it improves the rise time at the output when the input goes down. This is because the time constant for discharging the BJTs capacitance is determined by the 47k resistor(s) - single vs. parallel.
R1 absent? Open circuit?If R1 were absent, then it wouldn’t, but with R1 in circuit R2 sets the switch on threshold.