How does a pull up resistor work on a transistor?
Thus the transistor turns ON to pull the output to a LOW level. The size of the pull-up resistor depends on the connected load and the voltage drop across the resistor when the transistor is OFF. When the output is LOW, the transistor must be able to sink the load current through the pull-up resistor.
How is the emitter current represented in a transistor?
The emitter-base junction (n-p junction) is forward biased and the base-collector junction (p-n junction) is reverse biased. The emitter current IE direction which is represented by an arrow shows that the emitter current is flowing outwards the transistor.
Which is the conventional current direction of a PNP transistor?
The conventional current direction of npn and pnp transistor is shown in the below figure. Consider the pnp transistor as shown in the below figure. The emitter-base junction (p-n junction) or emitter junction is forward biased and the base-collector junction (n-p junction) or collector junction is reverse biased.
How is a pull up resistor connected to a Vcc supply?
This condition means that their output is either grounded when LOW, or floating when HIGH, so an external pull-up resistor, (Rp) needs to be connected from the open-collector terminal of the pull-down transistor to the Vcc supply.
What does a low side transistor switch mean?
Low-side transistor configuration When the transistor is connected to ground, that means the load is between +V and the transistor. Since the transistor is switching the path to ground or is sitting on the low side of the load, it is called a low side switch. Typically these use an NPN BJT or an N-Channel MOSFET.
Do you need a pull down resistor for NPN?
Since an NPN transistor’s base is not a high impedance point like a MOSFET or a JFET, and the H F E of the transistor is less than 500, and at least 0.6V is needed to turn the transistor ON, a pull-down resistor is not critical, and in most cases is not even needed.
Can a p channel be used on a low side transistor?
For a P-Channel MOSFET, the source connects to the voltage source, and the drain connects to the load’s positive side. Like with the low-side, you probably want to use an enhancement mode MOSFET. Keep in mind that you may never find a depletion mode P-Channel.