Table of Contents
Why is a resistor connected before ground?
The resistor to ground (1 Meg) prevents the input from floating whenever no input is connected. It also sets the input impedance, which typically is desired to be be fairly high relative to the source impedance.
Do we need to ground the unused input for AND gate?
To ensure that the gates are not left floating they should be connected either to ground or to the supply rail. Often it will not matter which is used, unless it is an input on a used function when the required input, either high or low would mean connecting it to the supply rail or ground respectively.
Do resistors go to ground?
They operate using the same concepts, except the pull-up resistor is connected to the high voltage (this is usually 3.3V or 5V and is often refereed to as VCC) and the pull-down resistor is connected to ground. The current flows through the resistor to ground, thus the input pin reads a low state.
Why pull-up and pull-down resistors are used?
To ensure the values of an I/P is always in a known state, pull up and pull-down resistors are used. The main function of pull-up and pull-down resistors is that the pull up resistor pulls the signal to high state unless it is driven low; and, a pull-down resistor pulls the signal to low state unless it is driven high.
Why should unused inputs be handled properly?
Because CMOS logic has a very high input impedance, any open input might result in a false output value due to the influence of a surrounding electric field. …
What is unused input?
Real unused logic inputs are ones whose logic state does not affect the particular application required—these should be connected to fixed Logic 0 or Logic 1 potentials and not left floating6.
What is the purpose of a capacitor to ground?
The capacitors to ground form a low-pass filter for the lines they’re connected to, as they remove high-frequency signals from the line by giving those signals a low-impedance path to GND. See this question.
What is the purpose of a pull down resistor?
What is Pull-down Resistors. Similarly to pull-up resistors, pull-down resistors ensure the voltage between VCC and a microcontroller pin is actively controlled when the switch is open. However, instead of pulling a pin to a high value, such resistors pull the pin to a low valued instead.
Why do we need a resistor between the gate and source?
The resistor to ground, or more generally between the gate and the source, is needed in circumstances where the thing that is driving the FET’s gate may be high-impedance when the power for the FET’s load is present. For example, if you are driving the circuit with an output pin of a microcontroller, this is a very common situation.
How does a resistor to ground work in a circuit?
The resistor to ground pulls stray voltages to ground and does not allow the FET to turn on until you apply a deliberate control voltage to it. Because there’s voltage and current then there is a voltage drop across the resistor, putting the signal voltage firmly on the gate and controlling the FET.
What is the difference between a pull up and pull down resistor?
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.
Why does a pull-up resistor create a logic “1” condition?
The result is that as there is very little input current into the input of the logic gate, very little voltage is dropped across the pull-up resistor so nearly all the +5V supply voltage is applied to the input pin creating a HIGH, logic “1” condition.