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Questions tagged [pnp]

A type of bipolar transistor comprised of p-type semiconductor in contact with n-type semiconductor which in turn is in contact with a p-type semiconductor -> thus PNP. The transistor has three terminals, the Emitter, Base and the Collector. Current injected into the base controls the flow of current from Emitter to Collector enabling amplification and switching.

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Understanding a PNP/NPN LED schematic

I bought and soldered a dirt-cheap flashlight kit from China. I'd like to understand how it works, though - specifically, why it uses a combination of a PNP and an NPN transistor (schematic from the ...
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75 views

PNP Transistor Switch for Relay

simulate this circuit – Schematic created using CircuitLab Hi, I have a low battery detection circuit here. When the voltage of the battery goes below 10.5, I have an LED flashing (Uses the ...
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31 views

What does this ɣ constant relate to in the carrier motion of BJT

What does the constant ɣ represent in the following carrier motion of an PNP transistor? So I see three components for the base current. 1) According to the illustration I can see that some of the ...
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ws2811 pnp driver [duplicate]

I am going to drive 9 RGB leds with a WS2811 LED Driver and NPN transistor as a switch. Can you please check my schematic for mistakes or advice?
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65 views

Converting earth signal to 5 V square wave

I am in the automotive industry. I am working on a little project, where the engine computer originally uses MOSFET to drive an earth to charge up an ignition coil, and by cutting the earth, it fires ...
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62 views

Transistor functionality in a given schematic

Can anyone tell me what is the functionality of the transistor in this schematic ?
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125 views

555 IC - Transistor Tester

Why are Pins 7 and 5 floating for this 555 IC and how does an NPN and PNP transistor when connected to E B C act a switch? Without the use of Pin 7 surely the capacitor cannot discharge which would ...
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24 views

Selectable sink or source Input

I'm looking for a circuit that I can add to a universal Input board that will be able to handle a 5-24v input PNP or an NPN 0v signal that I can connect to my arduino. I was considering using an ...
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32 views

How to activate a solenoid using TSOP4838 IR receiver

I have a TSOP4838 whose output is 5v normally and 2.5v when I press a button on my DVD remote. I wish to activate a solenoid when the DVD remote button is pressed. The circuit is is powered by a 9v ...
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66 views

Transistor latching circuit

I have made the following circuit from a few online sources, it is very basic but uses two NPN transistors to make a latching circuit that toggles when either push button goes to ground. My Falstad ...
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1answer
61 views

PNP Transistor - Use IC 555's internal resistance as pulldown?

I have a circuit that uses a PNP transistor to enable or not the current to flow and turn on a LED. The point is, is it a good engineering practice to conect the base of the transistor to the Vcc of ...
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110 views

Trouble turning on relay using PNP transistor

I am having problems turning on this relay: https://omronfs.omron.com/en_US/ecb/products/pdf/en-g6qe.pdf Using a transistor whose base is connected to a digital signal of an Arduino Nano. The ...
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79 views

Finding the broken cicuit in an Xor Gate

I am new to this particular stack site but I feel that this is the most appropriate place to ask my question. -Background- I've been following an online web course called Nand2Tetris that takes you ...
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1answer
47 views

Doing KVL on PNP BJT

I'm trying to find the voltage at the emitter and i use the property they give me of the absolute value VBE where in the book its equal to the small AC signal plus the DC VBE ( in this case that small ...
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36 views

Using a PNP to enable a NPN current source not yielding expected current

Hi I am trying to switch on a brake light with a reed switch. The load is a 12v (0.1A) LED bike light. The following circuit works in the sense that the light comes on when the magnet moves away from ...
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1answer
46 views

PNP array TD62783 output is not closing correctly when input signal goes down

I have TD62783 powered from 12V rail, inputs are driven from 5V rail by HC540. Each output has bunch of leds on the other side along with constant current sink (multiplexed 7 segment display). IC18/...
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2answers
129 views

555 timer circuit switching automotive solenoid with PNP & NPN switching transistors

I am trying to design a 30 second timer circuit to switch an automotive solenoid that draws about 0.8 amps, and need some help please. StackExchange posts have been very very helpful so far, and by ...
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51 views

Confusion with 555 transistor relay driver

This is probably schoolboy stuff, but before I construct it ... A 555 will output almost the supply rail, or down to zero. A transistor attached to that, with a relay on collector can drive a 12v ...
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3answers
96 views

PNP Transistor with low base current

I designed a PCB with the following schematics. simulate this circuit – Schematic created using CircuitLab The circuit uses a MAX6369 external watchdog timer which has an open-drain output(...
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56 views

PNP darlington pair calculations

I have a 20ohms discharge resistor connected to my PNP darlington pair. I have simulated the circuit in my mobile (every circuit app).please find the attachment for circuit. But here I'm unable to ...
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2answers
108 views

Calculation of base current

Could you tell me how to find Vd and Vb in the schematic please? Is the PNP in saturation or linear mode? I found Vb, with Vbe = Vb - Ve, then Vb = Ve -Vbe. To find the mode of the pnp, I need to ...
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119 views

DC current gain in complementary transistors

In Class-B amplifiers complementary PNP-NPN transistors are used, e.g. TIP2955 and TIP3055. https://www.electronics-tutorials.ws/transistor/tran_3.html says that They both have a DC current gain, ...
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83 views

PNP and NPN transistor characteristics for this project (see link inside for schematic)

I'm working on this project https://github.com/diyhue/Devices/tree/master/HueDimmerSwitch I would ask which characteristics I need to keep in consideration to choose that two NPN and PNP ...
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1answer
94 views

Need help with three-stage transistor amplifier in LTSpice

I am currently attempting to design an amplifier in LTSpice for an E1 project. My professor tends to emphasize analysis of these circuits, so he hasn't really given us any kind of a design process to ...
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94 views

Which region is the transistor operating at?

PNP and NPN transistors in the circuit have identical Is values. Based on the PNP transistor is connected to a DC voltage source. k = 1.38064852×10-23 J/K qe = 1.60217662 ×10-19 C Is = 0.69 fA at 17°...
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77 views

Need help understanding PNP Base into NPN Collecter circuit for LED Array

I am a novice in circuitry and I'm trying to make an 8x8x8 LED Cube using an instructables guide for a school project. I have ordered all the parts and was testing the grounding circuit for each layer ...
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160 views

PNP BJT small signal model

I have been solving BJT circuits on my textbook and stumbled upon a PNP BJT small signal model question. It asks to build the small signal model of a PNP transistor circuit. When I checked the ...
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3answers
198 views

Switching Relay with NPN and PNP transistors

I'm designing a locker system using Arduino. Due to system requirement, two IOs will be used control the relay, and only when two IOs are ON, then the relay will be triggered. PNP = BC807 NPN = ...
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29 views

Voltage alarm with LT1017

With help of this site, I have redeveloped my voltage alarm circuit (see my previous question for the history). I started off with an 741 Opamp and it did not work as I wanted it to work (Thanks for ...
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1answer
146 views

What's the purpose of using PNP transistors on I2S bus?

What could be the reason of using these 3 PNP transistors on I2S bus (LRCK, BCK and DATA pins)? The DAC used in this schematic is PCM5102. I know for sure that this DAC would work without these ...
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323 views

PNP Transistor switch circuit

I have been learning about transistors a lot lately. Following that I have managed to design a simple circuit that uses PNP transistor as a switch. Basically this is going to be a door alarm where if ...
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1answer
76 views

Is pulling current from Collector to Base allowed? (PNP transistor)

I am building a P-Mosfet gate driver and I have a question regarding the behavior of a PNP transistor connected in this way: This circuit might look pointless, but it's a good representation of a ...
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2answers
225 views

PNP load switching circuit that uses opposing PNP transistors

Background: This circuit uses two input signals to create a 0, 2.5, or 5V output signal that switches ON/OFF periodically to control for example an LED. I saw a transistor circuit example that had ...
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1answer
361 views

High voltage linear regulator (with pre-regulator)

I need to build a linear voltage regulator like this: The problem with the usual linear regulators (LM317, LM337, ..) is the limited voltages they can withstand. I have taken inspiration from a ...
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4answers
249 views

Toggle two LED status lights with two transistors

I have an input that is either floating, or grounded. The switch is fixed, it's either open or closed. Ie, I can't replace with a double throw. Here is the schematic / sim. If the switch is closed, ...
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1answer
56 views

Enable one or two of the same output via switch (minimalist schematic)

I'm making a PCB and my real estate is limited. I am using an AT89C2051 microcontroller, and it only has one serial transmit output. What I need is a way to set whether the output from the serial ...
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3answers
352 views

PNP instead of NPN in series voltage regulator

I have a question regarding PNP transistor, since I am not very familiar with it. What would be the difference in the circuit below, if we switched NPN to PNP? Right now the output voltage is equal ...
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695 views

How to calculate this two transistors Constant Current Source circuit?

I came across a constant current source calculator at Electronic Product website:enter link description here For example, for a 13.5V input, 300mA output, it comes out the following parameters: <...
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142 views

What kind of fan filter is this?

This schematic is part of a fan controller. simulate this circuit – Schematic created using CircuitLab FAN_POWER: 3.3 V (or 5 V for higher loads) PW_FAN: goes to the fan What kind of filter ...
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121 views

How to double the collector current of a BJT in LTSpice?

I am trying to model a multi-collector lateral PNP in LTSpice. The link here suggests to put 2 PNP transistors in parallel and split up the IS into two parts. http://pallen.ece.gatech.edu/Academic/...
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5answers
411 views

Transistor toggle by NPN and PNP - how is it build?

I want to toggle between 2 devices using one GPIO 3.3v pin and powering them with 5v. I thought about using an NPN and PNP transistor, tying up the base and collector/emitter to 5v power supply. If ...
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2answers
104 views

Am I right with select of base resistor?

simulate this circuit – Schematic created using CircuitLab I did add the NPN 2N3904 because I want to put on sleep the Arduino. So I need to put LOW the GPIO when goes in sleep. This is a ...
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1answer
357 views

Mixed NPN and PNP H-Bridge DC Motor Driver

I've briefly looked at including an H-Bridge circuit in one of my designs and I see that most (if not all) have N-Type transistors (either Darlington or MosFets). This however needs two separate ...
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828 views

Can someone explain this microcontroller ADC interface (for reading solar panel voltage)?

I am trying to understand the functionality of a circuit found in TIDA-00121 (you can download the design file from here) I assume that this has to do with the fact that the PV is not directly tied ...
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1answer
61 views

Need a bit of guidance in regards to this PNP transistor question

simulate this circuit – Schematic created using CircuitLab Hello! I'm currently stuck trying to answer this question. The question asks for me to find the resistance of R2 for R1 to be at 4V ...
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6k views

What's the purpose of these two diodes in this circuit?

What's to point of using these two diodes? Can't you just replace them with a resistor?
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313 views

How to connect a PNP inductive proximity sensor to a PC? [closed]

I have a PNP metal proximity sensor. I am using it to test a door lock mechanism. I need a way to connect this sensor to a PC and make a user interface to show me the signals and the values. I haven'...
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2answers
757 views

NPN or PNP transistor for Common Cathode Seven Segment Display LEDs?

I've read a bit about this but there seems to be much ambiguity. When using common cathode seven segment display LEDs would you use NPN or PNP? Or can you use either? Can someone please give a ...
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1answer
140 views

Why is my RGB LED strip passing current through the transistor?

I am following this schematic: http://www.electronoobs.com/eng_arduino_tut13_sch2.php It uses a BD140 PNP transistor. I checked the wiring was correct. Basically, the transistor boosts the current ...
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0answers
71 views

Transfer function of loop-back bias circuit for RF amplifier

I am trying to implement a current mirror as part of a bias circuit for a RF amplifier. I want to do a transfer function of the bias circuit since it creates a loop from the amplifier fet drain to ...