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.
318
questions
0
votes
1
answer
31
views
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, ...
- 329
3
votes
2
answers
525
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, ...
- 33
2
votes
2
answers
124
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-...
- 91
0
votes
1
answer
61
views
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 ...
- 1,223
2
votes
0
answers
24
views
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 ...
- 21
0
votes
1
answer
53
views
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' ...
- 95
1
vote
3
answers
55
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 ...
- 91
1
vote
1
answer
66
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?
- 23
1
vote
1
answer
42
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 ...
- 13
0
votes
1
answer
62
views
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 ...
- 1
0
votes
1
answer
92
views
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 ...
- 972
0
votes
0
answers
25
views
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&...
- 1
2
votes
1
answer
95
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 ...
- 511
9
votes
2
answers
388
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 ...
0
votes
0
answers
18
views
Problem validating PMOS bias characteristics
I have built a PMOS device with Vt=-0.39 shown in the link below
Vs=1.8 Vg=-1.5
Vgs=-1.5-1.8=-3.3V
|Vgs-Vt|=|Vgs-Vt|=|-3.3-(-0.39)|=2.91>|Vds|=1.8
I get a result where no matter what is my source ...
- 159
3
votes
1
answer
128
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 ...
- 33
0
votes
3
answers
119
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 ...
- 328
4
votes
1
answer
96
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 ...
- 51
0
votes
2
answers
67
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 ...
- 205
2
votes
2
answers
133
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?
2
votes
1
answer
116
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 ...
- 275
7
votes
2
answers
326
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 ...
- 856
0
votes
0
answers
101
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 ...
- 55
1
vote
0
answers
26
views
How to calculate accumulation charge concentration (/cm3) as a function of dist. from the oxide-semiconductor interface in a MOS cap with n-type semi?
I am trying to calculate the accumulation charge concentration (/cm3) for the MOS capacitor with Au/TiO2/n-InSb, where n doped InSb is the substrate. So far the material I found focuses on p-type ...
0
votes
0
answers
67
views
Maximum resistance on P-MOSFET gate pull-up
I have a P-MOSFET between my lithium battery and load. The P-MOSFET will only conduct if the battery's voltage is above a certain threshold to prevent over-discharging. The circuit is as shown below:
...
- 1,223
0
votes
1
answer
98
views
What is the best and simplest way to switch on a boost converter with an Arduino?
I am trying to control a 24V load with a 5V Arduino pin. I once burnt an Arduino but couldn't find why. I am extra cautious now.
My new design:
On the left side of R4 there is an Arduino pin. On the ...
- 275
0
votes
2
answers
95
views
NAND output connected to P-MOSFET gate
I am connecting an NAND logic gate output to a Pchannel mosfet gate and intending under normal conditions to sink current into the NAND output. But there are two scenarios about this setup which are ...
- 1,223
5
votes
4
answers
396
views
Low-side NMOS switch circuit
I built this circuit trying to learn how to drive a single HY3912W MOSFET. In the simulator, it acts as I expect.
I built it.
When I applied 6V to VAG and 5V for 1-second pulse to PWM every time the ...
- 319
0
votes
0
answers
48
views
Delayed start-up with no current consumption after
I have a delay circuit. My sole purpose is to disable the input from the orange line for some time after the power is on. After that this portion of the circuit should not consume any current. Here is ...
- 275
0
votes
1
answer
112
views
Replacing a diode with a MOSFET for reverse spike protection
Due to thermal considerations I am trying to replace D2 in this answer with a P-MOS FET. Came up with this diagram:
The two D1 symbols are just one bidirectional TVS diode (missing symbol in ...
- 1,002
0
votes
1
answer
86
views
Optocoupler + MOSFET PWM amplifier timing issue
I want to drive a 12V, 1.5A valve from a microprocessor and also provide some isolation. The MCU outputs 3.3V logic, and I have this output going into a common source amp & also have a resistor in ...
- 313
1
vote
1
answer
61
views
Power selection with MOSFET
I have a question about PMOS load driver. When V1 is high then Vout should be 1.5 V and it is okay. But when V2 is high, Vout should be 3 V rather than 2.4 V.
Can anyone explain me why this 2.4 V and ...
- 149
0
votes
0
answers
116
views
Why is that the nmos and pmos in parallel "compensate each other"?
Why is that the nmos and pmos in parallel "compensate each other"?
I use the simulation and found both current through nmos and pmos goes up if voltage across drain and source goes up.
- 1
7
votes
2
answers
2k
views
Why do we need transmission gate for XOR (transistor level design)?
The following image shows a 6-transistor XOR circuit.
But I don't know why the last 2 gates are needed at all, the circuit can be simplified to:
Is there anything that prevents us from using the ...
- 77
0
votes
1
answer
78
views
P-MOSFET - voltage on a drain pin when fully off
I'm trying to implement high side switch using P-MOSFET with NPN driver. I will drive the whole switch with AVR GPIO running at 3.3V (3.3V GPIO label). KT231B9 (it'...
- 257
0
votes
3
answers
188
views
Water level indicator using CMOS inverter
I want to build the below circuit. The circuit has three levels to indicate water. low->o/p LED. Medium->O/P LED. High->O/P LED + Buzzer. Each level has two types of MOSFET; they work as CMOS ...
- 15
-1
votes
1
answer
120
views
Unknown MOSFET symbol
I came across the schematic symbol shown, and I am unsure of what the symbol in the green box is. It looks like a PMOS (yellow box), but it has the line before the gate. Has anyone seen this before?
- 47
1
vote
0
answers
154
views
Why choose pmos over nmos
In the attached schematic, there are two branches. The branch on the left has a pmos + nmos transistor. The branch on the right has two nmos transistors. The sizes of the devices were selected such ...
- 55
1
vote
1
answer
289
views
PMOS/NMOS current direction and digital logic
What happens when the PMOS source is connected to negative Vcc (-Vcc).
What I understand is that when the gate voltage is <=0 then the drain-source is connected. Normally I would expect current to ...
- 17
0
votes
2
answers
153
views
Operating of FET in linear region
I have some data and would need some help to design a schematic. My target is to deal with the inrush current. I have a supply voltage range of 25-42V. A capacitive load of 1500uf. So I would like to ...
- 77
2
votes
0
answers
175
views
Small signal analysis of MOSFET circuit
The other day I got the following exercise on one of my exams:
For those who don't speak German, for transistor 1 lambda is 0, but not for the others. The backgate-effekt should be neglected ...
- 245
1
vote
1
answer
201
views
What are the limitations of AC coupling a MOSFET gate?
I came up with this AC coupled half bridge for high positive and negative voltage output with logic level control that I cannot find in any resources about (probably due to wrong search terms):
It ...
- 159
0
votes
0
answers
75
views
Reverse Voltage Protection using PMOS: Bias Resistor selection
1.How to calculate the bias resistor value (100R in snip attached) ?.
2.Is the resistor value depend on Zener clamping value?
- 55
1
vote
2
answers
2k
views
How to determine which terminal of a MOSFET is source, drain or gate [duplicate]
I am a student and for my next exam, as part of the tasks, I need to identify which terminals (pins) of P and N type mosfet are gate, source and drain. I have an example photo here, but if possible, I ...
- 31
0
votes
0
answers
59
views
To turn a ratioed circuit into non-ratioed circuit, what should be the transistor sizes for proper operation of this circuit?
The circuit is at the bottom. I know it is a ratioed circuit however, how can I convert it to a non-ratioed circuit without adding two more PMOS transistors between Vdd and the other PMOSs. Also, what ...
- 173
0
votes
1
answer
50
views
High Voltage PMOS devices availability
Generic question for experts well versed in semiconductor device physics. Most of the high voltage power switching devices seen are N-Channel (Silicon and Silicon Carbide) with varying ratings. Is ...
- 87
0
votes
1
answer
151
views
Power switch PMOS controlled by button or Microcontroller (or both, with an OR circuit)
I´m trying to design an analog circuit to use a push button to turn on an MCU and then use it the same push button to change modes. A "one push button circuit". To achieve that, I used a ...
- 197
0
votes
1
answer
153
views
Will this work for power path?
My goal is to disconnect the battery while the device is connected to USB Input. However when the device is disconnected from USB power, the battery will be connected to the system load.
I am using ...
- 13
2
votes
1
answer
71
views
PMOS reverse supply
I'm a little confused, can someone explain to me why this circuit conducts?
I thought that the body diode of the PMOS was in reverse polarity and the source node of PMOS should be at 0V, but ...
- 57
7
votes
5
answers
4k
views
Can you drive a P-MOSFET as a high side switch directly from a microcontroller?
I have an engineering background, but close-to-zero practical experience with discrete electronic circuit design.
simulate this circuit – Schematic created using CircuitLab
Regarding the above ...
- 131