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What does a collector resistor do?
The purpose of the collector resistor Rc is to set the collector current Ic as well as the emitter- collector voltage Vce. In other words, Rc helps to set the transistor at the “operating point” of the ampli- fier. The purpose of the emitter resistor Re is to prevent “thermal runaway”.
What is the function of pull-up resistor in open collector gates?
Pull-up Resistor Summary A pull-up resistor connects unused input pins (AND and NAND gates) to the dc supply voltage, (Vcc) to keep the given input HIGH. A pull-down resistor connects unused input pins (OR and NOR gates) to ground, (0V) to keep the given input LOW.
What kind of resistor does open collector output have?
Suppose that an open collector output is outfitted with a “pull-up ” resistor– a moderate value resistor (typically 2.2k – 10k) connected to a positive power supply rail, say 12 V.
What happens when a transistor is connected to a collector?
This “turns on” the transistor, which means that if there is any voltage (above about 1.5 V) connected to the collector– that is, connected to the output of the SN7407N channel –current will flow from the collector, through the transistor to ground.
What happens when we add a pull up resistor?
If we add a pull-up resistor instead of a load we get a logic circuit; each transistor functions as a tri-state inverter, together making up a (in this case) 3-input NOR gate. If A, B, and C are all low, none of the transistors are conducting (i.e. on) which means the output is high due to the pull-up resistor.
How does a pull up resistor work in a logic gate?
With a pull-up resistor connected, the output still works in the same way as a normal logic gate in that when the output transistor is OFF (open), the output is HIGH, and when the transistor is ON (closed), the output is LOW. Thus the transistor turns ON to pull the output to a LOW level.