Questions tagged [pmos]

A p-channel metal-oxide semiconductor (pMOS) transistor which has has p-type carriers used in the channel. The channel is established by a negative voltage on the gate which inverts the substrate (NWell) under the gate which turns the device on. The term may also be used to describe logic circuits built around pMOS transistors.

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1answer
233 views

changing the threshold voltage by controlling the oxide thickness in a p-mos [closed]

Can we change the threshold voltage by controlling the gate oxide thickness in a p-mos?
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1answer
992 views

Channel doping change to control the threshold voltage in an NMOS

By increasing the P-doping in an NMOS, threshold voltage is increased. How does it happen? And why? And what elements do they use for this? can anyone give me a reference or explain?
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801 views

Set the threshold voltage of CMOS inverter to VDD/2 for both rising and falling edge: possible?

Using 0.35u technology (VDD= 3.3v, Vt=0.7, Tox = 0.7 nm), I am trying to set the threshold voltage of an inverter to VDD/2. If I set the width ratio of PMOS/NMOS to 5 (means the Width of PMOS would ...
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1answer
525 views

PMOS soft turn on slower current ramp up to capacitive load

I'm trying to understand MOSFET soft switch and I know the more common off-the-shelf configuration is to put the capacitor between gate and Vo. However, I'm trying to understand why I can't do it in ...
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1answer
1k views

Driving Inductive Load with MOSFET: N-Channel vs. P-Channel

Problem I am driving an inductive load from a microcontroller using a MOSFET. I have a current sense resistor in series with the load. I don't have much experience with transistors (should have paid ...
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1answer
80 views

How do you choose the exact width for PMOS/NMOS in your design?

I'm designing the following function: $$F = ((A'+B) \times (A+B'))'$$ This is the schematic: Now I know that in general PMOS width has to be 2-3 times that of NMOS width. But how do you decide ...
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1answer
224 views

Effect of increased leakage of PMOS in reversed inverter configuration

I have built the standard CMOS inverter in reversed configuration by putting NMOS on pull up side and PMOS on pull down side. This will work like a buffer but the the upper and lower bound of the ...
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1answer
492 views

How are PMOS equations different than NMOS's?

I have been googling about it and I see lots of different ways such as only flipping the signs (< becomes >) and switching variables (VGS becomes VSG). Some people even say just put absolute value ...
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2answers
534 views

Arduino pmos ZVP2106A as switch

I've got some ZVP201A PMOS transistor and I want to use one as a switch to control a little 5V 110-150mA light bulb with an Arduino. Here is my schematic: Is it correct? Is the ZVP201A the right ...
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1answer
493 views

Turning an NMOS with substrate terminal into a PMOS

Some NMOS's come with a substrate/bulk/body terminal so the "Source Voltage" referred to in literature then Substrate Voltage. Say then we short the gate to the drain and have the substrate take the ...
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3answers
983 views

Reverse polarity protection for a very low voltage devce

I want to add reverse polarity protection to a device which is powered by a single AA battery, so its voltage might go down to 0.8 V. Forward diode is too huge of a drop. I've already thought about ...
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1answer
585 views

Why is the current through the PMOS different to the NMOS?

I'm trying to alternate two LEDs with a shared PWM signal. When the signal is low D1 should conduct. When the signal is high D2 should conduct. I've created an LT Spice simulation of the circuit I ...
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1answer
231 views

Extrapolating Transistor DC Current Gain Graphs?

I'm working on a design which will use a BJT to switch 2 PMOS gates low to power 2 separate loads. I am going to drive the transistor from a NOR gate. From my transistors datasheet, I thought I could ...
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2answers
207 views

PMOS carrying more current than NMOS?

I dont know what is happening here. Both PMOS and NMOS have W=100*270nm L=180nm Vgs=1.8v vds=1.8v while NMOS is carrying only 14.19mA current, How can PMOS carry 15.97mA for the same size and ...
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1k views

How to size CMOS transistors

I am new to CMOS technology and I am trying to learn about CMOS logic gates. I have a problem with transistors sizing. As far as I could understand the main idea is to obtain equal rise and fall times....
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2answers
773 views

Will this high side p-mosfet switch circuit work?

I have two micro-controllers on a PCB. Both operating on 3.3V. One microcontroller will always be running. I need to cut off the power supply to other micro-controller sometimes. (This is not for ...
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1answer
1k views

Correct PMOS Vgs?

Please image attached. Is there a mistake on the solutuion as it seem that for the PMOS Vgs = Vs-Vg?? Isn't it supposed to be Vgs = Vg-Vs? Thanks
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1answer
436 views

Switching between two power supplies with a P channel Mosfet, Is VGS or VDS a problem?

So I am using the following circuit to switch between VIN 0-30v and USBVIN 5v. I thought I found the ideal solution until I realised the FET in the schematic only has a max VGS of 8V. But I don't ...
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3answers
1k views

What is the conventional circuit to control a P-MOSFET with MCU?

How a P-MOSFET works is clear, there is plenty of documentation on the web. But what's the standard circuit to use them as an ideal switch with an MCU is not that clear, in my opinion. I saw there ...
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4answers
4k views

P-channel MOSFET as high-side switch gets hot

So I'm trying to control my front lights of my car using an Arduino Nano. In total there are 14 lights (including foglights and blinkers etc.). I'm using two 75HC595 shift registers to control these ...
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2answers
2k views

Will this circuit protect my digital IOs from overvoltage conditions?

I have come up with the following circuit to protect my device's IOs from overvoltage conditions. simulate this circuit – Schematic created using CircuitLab The idea is that as soon as the ...
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1answer
2k views

NMOS/PMOS logic vs. CMOS logic

With PMOS and NMOS, one can deduce that it is off, if Vgs < Vt (NMOS) || Vsg < Vt (PMOS) id = 0. Now my question rests on the dependency of these conditions. I know proving condition 1 ...
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2answers
1k views

PMOS and NMOS in cut-off

I am confused regarding the voltages of NMOS and PMOS. For a NMOS, let us say it is in cut-off, thus making Id = 0. Then does that mean Vds = 0? I was initially under the assumption that Vds can be ...
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1answer
818 views

Threshold voltage of a pseudo nmos inverter

How can I find the Vm of a pseudo nmos inverter? Since I dont know the Vds of neither of my transistors I cant determine in which region they are. The circuit and some parameters are in that link. Wn ...
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4answers
3k views

3-pin MOSFET: P or N type?

This may be a silly one but I couldn't seem to find an explicit answer: with a 3-pin MOSFET, how do I determine whether it's an NMOS or PMOS? I'm making some assumptions here: I've already found the ...
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3answers
852 views

Switch (Relatively) High Voltage from Logic Level

The Situation: Basically, I would like to switch a load that requires 30v using a switch that cannot have more than 5v across it. More descriptively, I am trying to drive the anode of a VFD segment ...
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4answers
3k views

Phase margin analysis of a [diy] PMOS LDO [with LTspice]

I'm somewhat familiar with using LTspice to do phase margin analysis for a classic i.e. obvious negative feedback path opamp circuit; in fact I've done that analysis successfully for fixing real opamp ...
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1answer
663 views

Turning a PMOS Common Source into a Voltage Follower

So I have this PMOS Common Source. I thought I'd make it a Voltage Follower by simply pulling it down to ground. But when SPICE-ing, whatever value the pull down resistor I give, it just won't work as ...
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2answers
4k views

Why is CMOS fall time faster than rise time?

I've just started a computer architecture class, and the slides from a lecture says that the reason why fall time is faster than rise time is that the NMOS electrons have more mobility than PMOS which ...
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1answer
411 views

What is the circuit for the PMOS driver found in synchronous buck regulator ICs?

Some synchronous buck regulator ICs sport a NMOS lowside switch and a PMOS high side switch. I understand why these use a PMOS/NMOS pair instead of a NMOS/NMOS pair, but I can't seem to make sense of ...
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1answer
100 views

Strange oscillation when drving motor with PMOS

I am trying to drive a 24V DC motor with IRF5305 PMOS. I am generating ~300Hz PWM signal with an AVR microcontroller and level-shifting it to 12V-24V signal to drive MOSFETs gate. I need to use a PMOS ...
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1answer
2k views

NMOS and PMOS current sources

I'm really confused with the representation of PMOS device shown in the figure. Since conventional current direction in PMOS is from source to drain, shouldn't the current source be pointing upwards(...
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2answers
967 views

Single MOSFET Amplifiers [closed]

Why is it that when I see single MOSFET amplifiers or even complementary ones (one NMOS and PMOS), they would use what in single BJT amplifiers would be called "Common Emitter Amplifier". The output ...
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2answers
3k views

pmos transistor acting as pull down device

I have a simple question related to the pmos transistors. Why can't it be used to fully pull down a high voltage signal? Can somebody please help me to understand the electrical characteristics behind ...
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1answer
123 views

What are possible alternatives for a depletion PMOS

I need a fast reacting way of discharging a capacitor and I figure a simple depletion PMOS is what I need. The time at which the gate has to have a voltage to keep the depletion PMOS closed is not ...
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2answers
1k views

Precharging capacitors with P mosfet slew rate control - Unwanted turn ON

I am considering using a MOSFET to control the dV/dt rise (slew rate) when power is first applied to a DCDC power supply. This will hopefully resolve both a precharging issue I am having and the ...
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1answer
287 views

How to determine the voltage on the drain of a “hanging” PMOS

This is likely a simple question that has an equally simple answer. Below is the associated schematic. The problem I'm having is identifying what state M2 is in, and what the voltage is at Va. I know ...
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2answers
1k views

Drive DC Motor with H Bridge(H Bridge turns off too slow and problem with current monitor)

I have two questions about my circuit, drving DC Motor with H Bridge. The picture below shows my design and how I drive it with signals. For example, when I make the motor rotate forward, I give 'S1' ...
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2answers
911 views

How can I get this PMOS to turn off?

I have a 2V regulator circuit which is used to drive a microcontroller (EFM32G222F128). On the output of this regulator I have a delay switch type circuit (see image below) which is used in order to ...
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2answers
2k views

25V for PMOS switch VGS?

In a load supply using P-MOS, the input to source is 25V. We found unfortunately that the MOSFET we chose and soldered has only 20V maximum gate-source voltage. Although there are voltage dividers ...
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1answer
70 views

NMOS Channel Type

I've seen some conflicting information about the inversion channel for an NMOS device. Is NMOS n-channel or p-channel? And is the substrate n or p? I know PMOS is just the opposite for both and the ...
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2answers
179 views

switch OpAmp down to minimize power consumption

I'm currently designing a board which senses some stuff. The board is powered using a 6V lithium battery. According to my sensor+OpAmp logic I need to split the voltage into +/-3V. The circuitry to ...
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2answers
13k views

Create a CMOS circuit from a logic function [duplicate]

I have to create a CMOS circuit from the logic function: F= ~A + B (notA or B). I made the truth table but I'm stuck here trying to make the CMOS circuit. Any ideas anyone? Thanks! I know it's the ...
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1answer
689 views

CMOS technology, use a NMOS or PMOS as series switch?

A general question regarding switches in CMOS. Have a look at the schematic below (symplified current mirror) There is a input reference current, on/off switch, a PMOS mirror and the resulting output ...
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5answers
2k views

Replacing a Switch and Avoiding body diode conduction

I am trying to design a replacement for a 2:1 switch using FETs, which would be really easy if I didn't have to concern myself with the body diodes that are present on PMOS transistors. My scenario ...
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2answers
475 views

How to improve PMOS off time

I am trying to use PMOS SSM3J334R for charging battery. But I notice that my charging mosfet is getting heated even at less then 1A current. On checking waveform I found very bad off time of MOSFET. ...
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1answer
98 views

Spice simulation of a motor switching power supply

I'm designing a switching regulator for motor controlling, I have tried this circuit with spice but it does not work: The problem is that the voltage on the load of the regulator never goes down, as ...
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3answers
3k views

Using a P-channel MOSFET as an on/off switch

The project I want to build is shown below. I want to operate the P-channel mosfet on and off with variable frequency from 20-100Hz and I choose P-channel to do this so that the +350V will not be ...
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1answer
2k views

Adding hysteresis to MOSFET used as a switch

I have a low-voltage detection circuit which I use to trigger one of two LEDs (green, and red) that is powered off of a +9V battery cell. As the battery discharges, its output voltage decreases, until ...
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2answers
1k views

PFET to turn on/off system power

I have a Raspberry PI board connected to some external circuitry, and am using Microchip MCP23008 I2C GPIO expander chips to control external LEDs and motor circuitry. One important part of this ...