When to use pull up or pull down resistors?

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.

How should a pull-up resistor and a button be wired?

One pull down resistor is connected to the first input of the AND gate. The pushbutton is connected to the positive voltage, and then, a pull-down resistor is connected to GND. If the push button is not pressed, AND gate input will be low.

Why do we use pull up resistors?

In electronic logic circuits, a pull-up resistor or pull-down resistor is a resistor used to ensure a known state for a signal. A pull-up resistor effectively establishes an additional loop over the critical components, ensuring that the voltage is well-defined even when the switch is open.

How are the pull up and pull down resistors connected?

By using these two pull-up resistors, one for each input, when switch “A” or “B” is open (OFF), the input is effectively connected to the +5V supply rail via the pull-up resistor.

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 is the maximum pull up resistor for a logic gate?

By knowing the information above, we can calculate the maximum pull-up resistor value required for a single TTL 74LS series logic gate as: Then using Ohms Law, the maximum pull-up resistance required to drop 3 volts for a single TTL 74LS series logic gate would be 150kΩ.

Can a TTL gate be connected to a pull up resistor?

Two or more open-collector outputs of TTL gates can be directly connected together and tied through a single external pull-up resistor. The result is that the outputs are effectively AND’ed together as the combination behaves as if the gates were connected to an AND gate. This type of configuration is called wired AND logic.

When to use pull-up or pull-down resistors?

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.

Is a gate resistor necessary?

Misconception: You don’t need resistors on the gate Of course any time a resistor is shown in a schematic, people get worried about what complicated formula is needed to determine its value. For slow switching applications, like below 10 kHz, the resistor value doesn’t matter.

How do you calculate pull-down resistors?

To calculate the pull-down resistor value, it’s slightly different from the pull-up resistor value. Knowing that current is 100uA, we’ll take 0.5v as our pull-down voltage since the input is 0.8v. Thus, applying our R = V/I once again, but this time we don’t have to minus, so our formula remains constant.

What is a pull up or pull-down resistor Mcq?

Explanation: A pull-up or pull-down resistor is used to remove the full output drive on the output pin. It also gives a feeble current through the pull-up to a resistor.

How do you calculate pull down resistors?

Why pull-up resistor is required for port p0?

Why do we need to pull up a port 0 in 8051? – Quora. Since there is no internal pull-up resistor for Port0. It’s tri-state and basically tri-state is a condition of ambiguity where we can’t predict it’s logic level. In order to remove the condition of ambiguity, we add external pull-up resistor to it.

Do MOSFETs need resistors?

You do not strictly need a base resistor. Not only do MOSFETs not have bases (they have gates), but the gate is (very) high impedance. Except when the MOSFET is changing states, the gate current is essentially zero.

Why does I2C need pull-up resistor?

As discussed in the I2C Basics module, the resistors that are commonly seen on I2C circuits sitting between the SCL and SDA lines and the voltage source are called pull up resistors. A pull up resistor is used to provide a default state for a signal line or general purpose input/ouput (GPIO) pin.

What does a pull down resistor do on a circuit?

The pull-down resistor which is connected to the ground or 0V sets the digital logic level pin to default or 0 until the switch is pressed and the logic level pin becomes high.

What is the maximum pull up resistor for a logic gate?

By knowing the information above, we can calculate the maximum pull-up resistor value required for a single TTL 74LS series logic gate as: Then using Ohms Law, the maximum pull-up resistance required to drop 3 volts for a single TTL 74LS series logic gate would be 150kΩ.

How big of a pull up resistor do I Need?

The pull-up resistor’s actual value depends on the impedance of the input pin that is closely related to the pin’s leakage current. Based on the two conditions above, for pull-up resistors, you need to use a resistor that is at least 10 times smaller than the value of the input pin impedance.

How many pull up resistors are used in a NAND gate?

Two push buttons are used as an inputs to the AND gate. The pull-up resistor value is 10 kilo Ohm and the remaining components are 330 Ohm resistor and LED. The 330 Ohm resistor is connected in series to limit the current to the LED The circuit diagram of the NAND gate using 2-pull-down resistors at the i/ps to the NAND gate is shown below.