What is meant by pull down transistor?
Similarly for input high, NMOS is ON, PMOS is OFF. The output is shorted to ground via NMOS. Hence we say, "output is pulled down to ground", hence the name pull down transistor for NMOS. Its withrespect to the output voltage level that we use the phrases "pull up"/"pull down"
A pull-down resistor works in the same way but is connected to ground. It holds the logic signal near zero volts when no other active device is connected. The value of a pull down or pull up resistor will vary depending upon your specific devices involved.
- The positive end of a diode is called the anode, and the negative end is called the cathode. Current can flow from the anode end to the cathode, but not the other direction. If you forget which way current flows through a diode, try to remember the mnemonic ACID: “anode current in diode” (also anode cathode is diode).
- Think of a diode as a one-way street for electricity. When the diode is in forward bias, the diode allows traffic, or current, to flow from the anode, towards the cathode leg. In a reverse bias current is blocked so there is no flow of electricity through the circuit.
- The PN junction diode is a two terminal device, which is formed when one side of the PN junction diode is made with p-type and doped with the N-type material.
Pull up is where you place a resistor between a signal and +V, pull down is pulling it to ground. Here, you can see that when the switch is open, in the pullup scenario the input pin will read high, but for pull down it will read low.
- Similarly for input high, NMOS is ON, PMOS is OFF. The output is shorted to ground via NMOS. Hence we say, "output is pulled down to ground", hence the name pull down transistor for NMOS. Its withrespect to the output voltage level that we use the phrases "pull up"/"pull down"
- In electronic logic circuits, a pull-up resistor is a resistor used to ensure a known state for a signal. In this case, when the switch is open, the voltage across a pull-up resistor with sufficiently low impedance vanishes to the effect that it looks like a wire to VCC.
- Instead of outputting a signal of a specific voltage or current, the output signal is applied to the base of an internal NPN transistor whose collector is externalized (open) on a pin of the IC. The emitter of the transistor is connected internally to the ground pin.
Updated: 26th November 2019