# Why Does PMOS Pass Weak Zero?

## What happens when an NMOS is connected to VDD and a PMOS to VSS?

If VDD is connected to NMOS, it outputs weak logic 1 and when VSS is connected to PMOS, it passes weak logic 0 due to threshold drop.

So, it acts like a buffer with degraded outputs.

When these are connected in series, the output further degrades..

## Why is the size of PMOS greater than NMOS?

NMOS has electrons as majority charge carriers and PMOS has holes as majority charge carriers. … Electrons has mobility ~2.7 times higher the holes. (The main reason behind making PMOS larger is that rise time and fall time of gate should be equal and for this the resistance of the NMOS and PMOS should be the same.)

## How many transistors might bring up latch up effect in P well structure?

Two transistorsExplanation: Two transistors and two resistances might bring up the latch-up effect in p-well structure. These are associated with p-well and with regions of the substrate.

## Which color is used for N diffusion?

GreenStick Diagram Colour CodeP diffusion:Yellow/BrownN diffusion:GreenPolysilicon:RedContacts & Taps:Black

## What is CMOS logic?

A logic IC using a CMOS circuit configuration is called a “CMOS logic IC.” In this circuit, the gate current flows only when the MOSFET is switched on and off, and the gate current hardly flows in the steady state. ICs that use CMOS circuits can form logic circuits that consume less current than in the case of TTLs.

## Which type of contact cuts are better?

Which type of contact cuts are better? Explanation: Buried contacts are much better than butted contacts.

## What is the condition for saturation *?

What is the condition for saturation? Explanation: The condition for saturation is Vds = Vgs – Vt since at this point IR drop in the channel equals the effective gate to channel voltage at the drain.

## What is CMOS NAND gate?

CMOS NAND Gate It consists of two series NMOS transistors between Y and Ground and two parallel PMOS transistors between Y and VDD. If either input A or B is logic 0, at least one of the NMOS transistors will be OFF, breaking the path from Y to Ground. … Hence, the output will be logic low.

## Why does PMOS pass weak 0?

So node out reaching to a potential less than Vthp turns off the PMOS. So the maximum voltage level that the output node can be discharged to is |Vthp|. So an NMOS passes weak 1 and PMOS passes weak 0 whereas no such situations occur when an NMOS passes 0 and a PMOS passes 1.

## Why pass transistor passes Strong 0 and weak 1?

NMOS pass transistor passes Strong ‘0’ but weak ‘1’  An NMOS pass-transistor can pull down to the negative rail, but it can pull-up to a threshold voltage below the positive rail.  => It can output a strong zero, but a weak one. …  So node out reaching to a potential more than VDD- Vt,n turns off the NMOS.

## Why PMOS is always connected to VDD?

This is the reason it is connected to Ground. … Because the voltage between the Ground and the Source in the NMOS transistor has to be positive, so the logical choice is to connect the Source to the ground. In PMOS, the voltage between the Gate and the Source has to be negative, so you connect the Source to VDD.

## Which CMOS gate is faster?

Which gate is faster? Explanation: NOR gate is faster. NAND is more complex than NOR and thus NOR is faster and efficient.

## What is the difference between pass transistor and transmission gate?

Transmission-Gate | Pass-Transistor-Logic i.e. NMOS devices passes a strong ‘0’ but a weak ‘1’ while PMOS transistors pass a strong ‘1’ but a weak ‘0’. The transmission gate combines the best of the two devices by placing an NMOS transistor in parallel with a PMOS transistor as shown in Figure below.

## Which is faster PMOS or NMOS?

NMOS are considered to be faster than PMOS, since the carriers in NMOS, which are electrons, travel twice as fast as holes, which are the carriers in PMOS. But PMOS devices are more immune to noise than NMOS devices.

## What is Latchup CMOS?

What is Latchup: Latchup refers to short circuit formed between power and ground rails in an IC leading to high current and damage to the IC. Speaking about CMOS transistors, latch up is the phenomenon of low impedance path between power rail and ground rail due to interaction between parasitic pnp and npn transistors.

## Why substrate is lightly doped?

O). The p-type doped substrate is only very lightly doped, and so it has a very high electrical resistance, and current cannot pass between the source and drain if there is zero voltage on the gate. … When the gate electrode is positively charged, it will therefore repel the holes in the p-type region.

## Why PMOS Cannot be used as pull down network?

Here pull up is nMOS transistor and pull down is pMOS transistor. When logic 1 is applied as input, nMOS transistor turns ON and PMOS transistor turns OFF. Hence, the output should get charged to Vdd. … But due to threshold voltage effect, pMOS is not capable of passing good logical 0 at the output.

## What is the condition for non conducting mode?

What is the condition for non conducting mode? Explanation: In enhancement mode the device is in non conducting mode, and its condition is Vds = Vgs = Vs = 0. Explanation: nMOS transistors are acceptor doped. Acceptor is a dopant which when added forms p-type region.

## What happens if we interchange PMOS and NMOS in a CMOS inverter?

Answer. When pmos and nmos are interchanged in CMOS inverter it gives a buffer with weak output states. If again the PMOS transistor be from Vcc down so when its input goes low it passes and pulls the output high opposite to the NMOS one be at ground so when input goes high then output goes low.

## What is threshold voltage of CMOS inverter?

Vth is the inverter threshold voltage, which is Vdd /2, where Vdd is the output voltage. The output is switched from 0 to Vdd when input is less than Vth. So, for 0

## Why do we use CMOS instead of PMOS and NMOS?

An advantage of CMOS over NMOS logic is that both low-to-high and high-to-low output transitions are fast since the (PMOS) pull-up transistors have low resistance when switched on, unlike the load resistors in NMOS logic. In addition, the output signal swings the full voltage between the low and high rails.