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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P-Channel MOSFET high side switch

I am trying to reduce the power dissipation of a P-Channel MOSFET high side switch. So my question is: is there any way in which this circuit can be modified so that the P-Channel MOSFET will ...
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5answers
8k views

P-Channel MOSFET Inrush Current Limiting

I have been searching EESE and Google for several weeks now for a solution to this problem, and while I found some proposals that seemed promising, the real-world implementation fell short of ...
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4answers
3k views

Why old PMOS/NMOS logic needed multiple voltages?

Why does old PMOS/NMOS logic needed multiple voltages like +5, -5, and +12 volts? For example, old Intel 8080 processors, old DRAMs, e.t.c... I'm interested in the causes on the physical/layout ...
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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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3answers
22k views

Is there a popular small signal PFET equivalent to NFETs 2N7000 or BS170?

Some days ago I was considering using a small signal P-Channel MOSFET in a design of mine, but could not find a suitable part. The specs I was looking for were something like the following: \$I_D = -...
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2answers
6k views

Reverse polarity protection - PMOS vs Schottkey diode

I have a circuit running from 2 AA cells in series, meaning I get 3.0V when fresh (or 2.4V if NIMH cells) and it goes down to 2.0V, that's when my circuit cannot function anymore (no DC/DC onboard). ...
11
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1answer
5k views

Where are the depletion PMOS transistors?

In school, I was taught about PMOS and NMOS transistors, and about enhancement- and depletion-mode transistors. Here's the short version of what I understand: Enhancement means that the channel is ...
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1answer
2k views

Explain the use of NPN and pMOSFET in this 8x8x8 LED cube

I've got part of a circuit diagram for an 8x8x8 RGB LED cube from http://www.kevindarrah.com. See the entire schematic. I'm having trouble working out how it does what it does. I know that a high ...
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1answer
6k views

Designing stable PMOS voltage regulator

As a follow-on to the question "Using forward voltage drop of diodes with linear regulator" I am looking into designing PMOS voltage regulators. General Topology A common problem with the intuitive ...
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3answers
834 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 ...
2
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1answer
3k views

PMOS Gate Driver using BJT

I'm (again) looking at high-side load-switching. The load shall be switched on with a controlled rise-time (=limited inrush current) and be switched-off quickly when a controller (not shown) detects ...
2
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1answer
482 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
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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2answers
705 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
64 views

Calculating resistors for an optocoupler controlling a pmos

I want to use a pmos (SI7157DP-T1-GE3, datasheet) as switch - controlled by an optocoupler (TLP291(V4GBTP,SE, datasheet) which is controlled by a teensy 3.6 (3V3 output voltage). Now I'm calculating ...
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2answers
883 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
76 views

P MOSFET turning on before gate threshold

I was simulating a P MOSFET, and for turning a P MOSFET on we need gate to Source voltage less then its threshold voltage. as per below simulation circuit at start VGS= 0, then there is no way mosfet ...