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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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65 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
33 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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33 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
36 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
91 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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46 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
84 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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46 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
102 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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103 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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3answers
71 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
73 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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2answers
81 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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1answer
62 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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1answer
106 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
153 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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1answer
26 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
119 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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1answer
214 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
72 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
197 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
248 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
182 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
257 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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2answers
547 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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4answers
136 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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1answer
109 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
359 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
102 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
301 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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2answers
812 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
57 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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7answers
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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1answer
276 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
611 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
127 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
68 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 ...
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3answers
717 views

Light up an LED with an NPN transistor in active low?

I have a circuit which is turned on at a logical zero. I would like to have a LED indicating this circuit is on, but I only have NPN transistors at this moment, which conduct when there's a logical ...
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4answers
426 views

How to safely measure VCEO or VCES of a transistor?

As an example, NPN Silicon Power Transistor TIP31 VCEO (Collector-Emitter Voltage) is rated at 40Vdc Maximum. I have many unknown transistors for which I would need to measure the VCEO. Many are power ...
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1answer
351 views

Inverting schmitt trigger with pnp transistors

I have a question regarding Schmitt Trigger. I am trying to design an inverting output (at UTP=Low, at LTP=High) Schmitt Trigger for an application. However, I need to use PNP transistors since the ...
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2answers
212 views

PNP transistor with audio signal output on collector is used to drive opto-isolator. How does it work?

I have tried assembling the circuit but it doesn't work. Now I need to understand how it works in order to debug it. The part that confuses me is: Channel 1 is a standard audio output from a ...
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3answers
612 views

Baker Clamp application for PNP Transistor

I have an issue related to Baker Clamp application for PNP Transistor. I know how to implement the Baker Clamp for NPN Transistor. However I do not know how to do it for PNP. So could anyone can ...
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2answers
183 views

12v PNP- switching with MCU

Hey I got a question about switching a 12V supply to a low power circuit with an MCU. My requiaments are: - switching has to be on the High side. - switch should stay "closed" when MCU is powered ...
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2answers
100 views

NPN-switching 4V with a 3.3V signal

I have a project where I need to switch the + side coming from the battery (single cell LiPo) to a consumer (ESP8266) with a 3.3V signal (common ground). I have loads of NPN and PNP-transistors here, ...
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2answers
69 views

Solenoid driver heating issue [closed]

This is regarding an automotive transmission control module(TCM) solenoid driver. The schematic diagram of the driver is very similar to the below image. Only difference is the TCM has the low side ...
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1answer
355 views

Using 2N2222 as level shifter for TIP127: simulation works, circuit does not [closed]

I'm building an H-bridge with complementary Darlingtons, TIP122 and TIP127, as they are cheap and the nearby shop has them (i know about the high power dissipation, it doesn't matter), and i found ...
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2answers
209 views

Problem testing a DC Motor Controller

I want to build a robotic arm for a project, but I got stuck while testing the motor driver on the breadboard. I have followed the instructions from this instructable: https://www.instructables.com/...
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3answers
131 views

Understanding constant current circuit

I've been learning about different constant current circuit designs and just recently stumbled upon this one. All I know is that the highlighted resistor is the load resistor and when varied, like a ...
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1answer
711 views

Water level indicator with PNP transistor

I wanted to create a circuit that Lit's up an LED when water level rises to a certain level. I have created the following schematics following the https://www.electronicshub.org/water-level-alarm-...