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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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For MOSFET amplifier circuit with drain current source, given \$k, V_t, V_A\$ find \$V_D, I_D\$ [closed]

Somebody closed this question, saying it lacked focus. However, I disagree with this, since it focused in finding which equations to derive in the DC analysis of the given amplifier with DC source. I ...
Mamamama's user avatar
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Diode Connected PMOS Doesn't Fully Activate

I'm very new to electrical and am trying to understand a diode connected PMOS. I am supplying 3.3V to the source and have tried varying loads after the drain of 220, 10k, 100k, 650k, 1.2M ohms. What I ...
Jared's user avatar
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High side PMOS FET for pre-charge circuit

I'm trying to charge a large capacitor bank (C1) with a resistor (R1) and when it's mostly charged, activate a p-FET (M1) using an op-amp comparator. I built a PCB but the p-FET isn't turning on. I ...
Ben's user avatar
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When a typical fixed output voltage LDO is unpowered, is the output pulled to ground or is it floating/high impedance?

I am wondering since in a design the gate of a PMOS is pulled up by the output of a voltage regulator. Since the source of the PMOS still sees voltage on its source in that condition, I don't know if ...
TnF's user avatar
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Why simulation of single NMOS/PMOS on LTspice has big difference with manual calculation using Level 1 Standard Parameters?

I am researching the mode of operation on PMOS and NMOS using Level 1 standard parameters. This is the information of the NMOS circuit to be designed. Using transistor model level 1 parameters, ...
CJ. T's user avatar
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How to interpret MOSFET connections and voltages

I have a few simple question about MOSFETs on how to interpret their symbols and how the pins and gate voltage are defined. • I see symbols with the Source shown on the top and Drain on the bottom, ...
McKendrigo's user avatar
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4 answers
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Why does powering an ESP32 directly from a power supply work, but when powering through a pMOS it doesn't?

I have this circuit which is used to switch on an ESP32 from another MCU. The GPIO goes on, the nMOS circuit becomes closed and the pMOS gate voltage drops to 0 which then also closes to allow the 3V3 ...
verpas's user avatar
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Clarification on the Application of a p-Channel MOSFET in a Circuit Diagram

I am seeking clarification on the application of a p-channel MOSFET as illustrated in the diagram below. Could someone please provide an explanation? In the diagram, legs 1, 2, 6, and 5 serve as ...
user23910965's user avatar
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1 answer
159 views

CMOS (Energy Supply of voltage) [closed]

Can someone please explain why, when \$ln\$ is transitioning from low to high, the energy supplied is \$C_{vdd}\cdot V_{dd}^2\$?
Timothy Garott's user avatar
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PMOS configured in common gate

This is an NMOS configured in common gate: I am trying to understand what a PMOS configured in common gate would look like. Would Vin and Vout be reversed in this case? So, would VDD be connected to ...
c.leblanc's user avatar
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How is the total gate charge of a MOSFET affected by the temperature?

For P- and N-MOSFETs, Vgsth will decrease (in absolute value) when the temperature rises. What is the impact of the temperature on the total gate charge for P- and N-MOSFETs? What is the order of ...
Rémi Baudoux's user avatar
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PMOS circuit Voltages doubt in LTSPICE

I am trying to understand basics about PMOS transistor such as understand Vth value when the transistor goes to saturation and permits the drain to flow completely. My circuit is this and the voltages ...
imt_blake's user avatar
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Microcontroller mosfet switch

There are three different processors in my circuit. These are STM32F401RCT6, ATmega328P and ESP32. I want to turn these processors on and off with the switch whenever I want. The circuit I created for ...
Emre Celik's user avatar
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9T SRAM Circuit Supporting 1-bit Multiplication

I was reading a paper that added a 3T NAND gate, consisting of two NMOS and one PMOS, to the regular 6T SRAM, achieving 1-bit multiplication. However, I'm struggling to understand how the NAND part of ...
BlueSun's user avatar
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2 answers
417 views

Load Selector/Load Switch

Following the provided schematic, my goal is to design a circuit that can determine the direction of a Pulse signal based on a control signal (CTL). To achieve this, I am utilizing two pmos ...
Nedou's user avatar
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Output level of common-source amplifier with PMOS load

Let's consider the common-source amplifier circuit above (left). This circuit does not have a well-defined output level. This part is easy to understand. In the book by Razavi, he says this "...
Leonhard Euler's user avatar
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5V 2 Rail ORing Power Switch Issue

I'm trying to create a power switch that toggles between two DC power sources. I have two 5V DC sources: one from an adapter and the other from a Type C VBUS port. The adapter takes priority, meaning ...
electroeso's user avatar
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PMOS + resistor \$I_{DS} - V_{DS}\$ curve

I'm trying to plot the \$I_{DS} - V_{DS}\$ graph for a PMOS and a resistor. I'm getting this so far: Weird thing is, what I should get (based on my course) should be something like : How come the ...
c.leblanc's user avatar
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6 votes
1 answer
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Why is the gate resistance of this PMOS so low? It should be very high

I'm looking for PMOS with BJT to drive a load (motor,) that is controlled by a microcontroller (IO_FET): The motor needs three amperes of current. I looked at the manufacturer's pages of the PMOS (...
Knowledge's user avatar
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How to make a PMOS work as a constant current source?

I have a circuit in which, the PMOS is biased to a voltage source, the gate voltage, V1, of the NMOS below varies based on the functioning of the analog circuitry before. Because of this, the current ...
Siva Sandilya's user avatar
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Electric-lock control via NMOS matrix

Currently I am working on the design that allows to control 8x8 electric lock matrix via PIC16F877A. As in comments for somebody it was not obvious (btw it was mentioned) I am using 64 electric locks ...
Alioth's user avatar
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High Side P-MOSFET Load Voltage

I ran into a problem during a circuit simulation. The circuit is rather simple: one P-MOSFET with a load. The MOSFET is acting like a high-side switch. My load is around 4-5 ohms. I noticed that the ...
Luka's user avatar
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2 votes
4 answers
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Need an explanation of how the circuit works

I came across this bidirectional switch circuit by Texas Instruments. I know how two MOSFETs configuration works but when I apply the pulse to turn it on and off the NMOS but it does not change its ...
Shamurov's user avatar
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Effect of multiplier on MOSFET region of operation

I am designing a wide swing cascode current mirror using PMOS. In the fig attached below, M4 goes into triode when I change the multiplier value. I need to output a current that equals 50*Iref. The ...
Arshiya's user avatar
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the inverter switching point

As we know the mobility of the "nmos" device is 3x greater than "pmos", and when we want to correct the switching point of an inverter for vdd/2 we usually change the W of the &...
Vahe Armenakyan's user avatar
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Unicorn Mode PMOS For Hurricane Flooded Golf Cart Controllers

We have saltwater flooded golf carts after hurricane Ian. Their old 0-5k Ohm throttle pots are shot, and replacing them is very expensive. The new throttle systems can be fitted more cheaply, but ...
Elkrat's user avatar
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1 vote
4 answers
326 views

Don't really know, why P-channel mosfet does not switch

I am currently working on creating a switch to control 24 V for BLDC. I am using esp32 to turn on and off the switch (3.3V logic). I intend to use P-channel mosfet, because I want to connect 24 V on ...
Dominykas's user avatar
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2 votes
1 answer
152 views

Protection for PMOS VGS rating

I am using PMOS as a switch to control 24V to deliver to load. When MCU drives the NMOS it is suppose to pull the PMOS gate to GND and turn-on so that load can get the 24V. This is what expected as ...
Brt's user avatar
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R5613L understandig what MOSFET to use

I want to add a battery-protection to my circuit including a switch to disconnect the battery from the rest. I found the R5613L from Nisshinbo (Manufacturer product site with datasheet). On page 26, ...
Lyoner's user avatar
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3 votes
2 answers
691 views

What happens when Vdrain is greater than Vsource in PMOS Transistor?

So as I understand, if Vsd = 0 in a pmos transistor, then the current flow should be zero, and the same goes for if Vs<Vd, now my question is, in what state will be the transistor i.e. cut-off, ...
Nemo Holmes's user avatar
2 votes
2 answers
175 views

Voltage drop of a p-channel mosfet

I am adding reverse polarity protection to my circuit. I can simply use a diode/schottky diode to do that; however, my main concern with a diode is its voltage drop. Therefore, I am considering the P-...
Alex's user avatar
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1 answer
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Battery isolation circuit with inverted logic

I asked a question some time ago in regards to preventing back charging my back-up battery question. I was just using a diode, but a circuit was suggested for more protection. It doesn't lend itself ...
Feynman137's user avatar
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Wide Swing PMOS Cascode Biasing

I would like to know if someone has designed a wide swing PMOS cascode biasing circuit (as attached in the picture) in 16nm FinFET, especially for IO devices having 1.8V supply. I see that ...
Daffodil's user avatar
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Wider width or more fingers for CMOS transistor to reduce conduction loss in syncrhonous buck converter?

For a project, I am trying to optimize my buck converter to obtain a power efficiency of 87 %. The non-optimized buck converter gives a power efficiency of 86 %. I try to size my PMOS 'power' ...
Kwok's user avatar
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1 vote
3 answers
417 views

Why do I need a pullup resistor at the gate when using a pmos as a high side switch

Very quick question: Assuming I am using a pmos as a high side switch and my supply voltage and the voltage at the gate I want to switch the transistor with (V_logic) are the same. I usually find ...
Axodarap's user avatar
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1 vote
1 answer
71 views

PMOS misleads immediately upon power on

I have encountered some problems. When I turn off S2, my PMOS will briefly turn on. Can anyone give me any advice related to this?
Iceeman's user avatar
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1 vote
1 answer
102 views

Current flow in PMOS when not active

how can it be that Q2 is active when VA and VB are HIGH? If I understand correctly, a current (shown in yellow) should flow... But that is in my understanding not possible because both NMOS are ...
BukkitDEV's user avatar
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P-MOS high side switch problem

I have designed a PCB that utilizes a P-MOS as a high-side switch to control a 48 V battery using the following circuit. The P3 connector is connected to a momentary switch and a 5 V LED. The intended ...
Hamed's user avatar
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High-side H-bridge, where low side is connected to a constant current source

I would like to couple a constant-current source with a high-side H-bridge and it seems to be way more difficult than expected. In the end, it is a constant current source from 0-10 mA with a voltage ...
HansPeterLoft's user avatar
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li1220 (chargered, 4.2v) battery power control with esp32 (2.7v gpio) using pmos

My project has two esp32 modules, one of which is the master and the other controls relays and other "peripherals". Please don't ask "why you need to turn the second esp32 on and off&...
Yelgurk's user avatar
2 votes
1 answer
314 views

Benefits/downside of discrete high-/low-side NMOS/PMOS and high-side bootstrap NMOS switching circuit

What are the key features or rather benefits/downsides of these discrete switching circuits in comparison: Low-side NMOS High-side NMOS Low-side PMOS High-side PMOS Boot-strap NMOS circuit The basic ...
Dakalaom's user avatar
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9 votes
2 answers
496 views

P-channel MOSFET gating circuit that passes voltages above 17 V

I'm designing a desktop PC motherboard with AMD Ryzen™ 9 7940HS. We have an extension board similar to this one that performs negotiations with USB-PD charger and provides 20 V constant voltage to the ...
Firas Abd El Gani's user avatar
3 votes
1 answer
327 views

P-channel MOSFET is always on (LTspice)

I've modelled an undervoltage lockout circuit that should trip when the voltage is around 7 V. Attached is an image of the circuit. At 12 V, the positive end of the comparator is less than the ...
dechair3's user avatar
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3 answers
191 views

What current flows through a Zener diode that is in parallel with the gate of a MOSFET?

I was reviewing this circuit and I can't figure out how much current goes through the Zener diode. I understand that it is there to protect the MOSFET gate against high voltages but how much current ...
WalterPH's user avatar
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4 votes
1 answer
247 views

Low quiescent current, 50V high-side PMOS driver

First, I never used Zener and BJT before, so if I made something stupid please explain, I'm eager to learn. The project is battery-operated and has 8 to 16 outputs with an individually selectable ...
GCarles's user avatar
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2 answers
127 views

Is there anything wrong with using large values for L/W for a PMOS?

Worked on a project recently for a linear circuit design course. Professor gave us the requirements to build a 5T OTA circuit which must have a gain of 30dB, unity frequency of 200kHz, etc. Designed ...
MFerguson's user avatar
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2 votes
2 answers
308 views

Driving a motor with a high-side PMOS switch. Does it need a flyback diode?

I'm looking to use a high-side PMOS switch to control a brushed DC motor. Is it necessary to add a flyback diode for this implementation? And if so, how/where exactly should it be added?
solderballz666's user avatar
2 votes
1 answer
192 views

Which consumes less current in microcontrollers: Always HIGH pins or always LOW pins?

I am driving a P-MOSFET (IRLML6402) with ATtiny24A microcontroller. This is a battery powered system; that's why ATtiny is always on sleep. I originally configured a BJT which is driven by the ...
CaveScientist's user avatar
7 votes
2 answers
456 views

What problem is solved by using a PMOS for reverse polarity protection instead of an NMOS?

Many resources suggest the use of a PMOS for reverse polarity protection instead of a diode, as it decreases losses. However, the characterstics of an NMOS are better than a PMOS, so why is using it ...
Anas Malas's user avatar
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0 answers
226 views

Totally misunderstanding how a PMOS works? PMOS not turning off

I'm trying to use a PMOS to inverse an on/off signal. This is for a battery powered application. VSNS pin is connected to MCU GPIO. By design the rotary encoder channels A/B (detent type) are always ...
Vulxcn's user avatar
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