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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How can I calculate the base current required for my multistage connected PNP transistor to obtain an obtain an output collector current Ic = 1.5A?

I need to design a circuit that provides an output of 11.5V with a current of 1.5A. This output is drawn from a TIP42 PNP transistor. The transistor gets its base input from a NPN2222 transistor. The ...
Coding247's user avatar
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5 answers
193 views

Red/green LEDs to indicate on/off

I am trying to build a circuit that drives a red LED when the relay is OFF and drives a green LED when the relay is ON. I found exactly what I was looking for, but it is for 9 V, and my circuit is ...
Paul STL's user avatar
9 votes
3 answers
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How does this garden solar light work?

I do not understand how this circuit powers on the load (the LED light). When the solar panel is inactive, i.e. it is dark, there will be a small current from emitter to base, and that will allow the ...
rosewater's user avatar
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Selecting PNP transistor replacement

In my circuit I have a discontinued transistor listed here: If I can not select a transistor rated 350 mA, would a change to the collector current pose any issues that may need compensating in my ...
Wes Ellgass's user avatar
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1 answer
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Using an NPN to detect high voltage and switch a battery circuit

I've done some simple PCB's but am not a real electronics designer so forgive stupid mistakes or stupid questions. I'm trying to detect a voltage range between 1-50 volts (VIN) as digital 'on' and ...
Oscar K's user avatar
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What are the tradeoffs between NPN vs PNP power transistors?

I'm working on a linear power supply design leveraging the uA723 regulator and I need power transistors to meet the current requirements (~2-3A). When looking looking through the regulators datasheet, ...
david's user avatar
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Pulling pin low through PNP BJT?

I'm using a battery charger/buck regulator IC that turns on if the pin named "shphld" is momentarily pulled low, and turns off if the pin named "shpact" is momentarily pulled high. ...
FloydPage's user avatar
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5 answers
258 views

How does this PNP transistor and P-channel MOSFET circuit work?

How does this PNP and P-channel MOSFET circuit work? How does the current flow? What are the voltage potentials at the nodes A, B, C and D?
ipving's user avatar
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Circuit analysis to understand how this circuit works - PNP

I am trying to understand how to get values at midpoint_diode and also at OUT. I understand this circuit is to step-down the voltage from Vin to something that is lower and also it used to have a ...
mdabdillah's user avatar
5 votes
2 answers
149 views

PNP pre-amplifier small signals study

It's always a pleasure to read this forum and this time I'm making the step to ask a question :) ! I'm currently working on a pre-amplifier for microphones based on a schematic seen in a famous sound ...
TooT's user avatar
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What causes a negative voltage dip on the collector of common emitter NPN circuit at turn-off?

Circuit diagram: simulate this circuit – Schematic created using CircuitLab Observed waveforms: (Yellow: 3.3V square wave in, Magenta: Collector output) When the input square wave goes low and ...
Unimportant's user avatar
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1 answer
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Different applications of NPN and PNP transistors in open collector circuits [closed]

Dear electronics enthusiasts, I recently encountered an interesting problem in electronic circuit design, related to the application of NPN and PNP-type transistors in open collector circuits. My ...
FredMorgan's user avatar
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2 answers
169 views

High side NPN and PNP switch

I have a high-side switch using a PMBT2222A NPN SOT23 and MMBT2907 PNP. Now my concern is if my configuration not beyond the specifications of the PNP transistor like not going out of their max ...
Citi's user avatar
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3 answers
75 views

PNP-transistor collector connected to the output of an op-amp?

Why is the transistor Q1 used in this configuration: collector is connected to the output of the op-amp U2? How does it work? I'm used to seeing that the output of the op-amp drives the base of the ...
dahaha's user avatar
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Using PFET to modulate power to load

A typical PFET reverse polarity detection circuit looks like this I was wondering if it is possible to use that same PFET to choke some power off to the load by adding a voltage divider using ...
learnvst's user avatar
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How is R3 drawing 0.6 mA current?

How is it that R3 draws 0.6 mA current in the circuit described below? The "divider" formed by R2-R3 may be confusing: R3's job is to keep Q3 off when Q2 is off; and when Q2 pulls its ...
user232591's user avatar
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3 answers
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Using an LDR and PNP transistor to automatically dim 12 V common anode 7-segment displays

I have designed and built a GPS time derived six digit digital clock using an Arduino. the digits are LED 2.3 inch common anode 12 V devices (because that's what I had!) and, after much work to drive ...
Mark Borchers's user avatar
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3 answers
119 views

555 timer getting power through output pin and powering itself

I'm currently working with a simple 555 variable frecuency aestable circuit, that switches a relay at the desired frecuency. Here is the schematic so you can understand my issue better: The circuit ...
fpp's user avatar
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2 votes
1 answer
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Why can't the resistor be 100ohms? [duplicate]

This is a portion of p.77 from The Art Of Electronics 3rd Edition. In the footnote, the authors say that R3 cannot be equal to 100ohms or Q3 will not turn on. Why is that? My understanding is that the ...
neutral.'s user avatar
1 vote
0 answers
48 views

Adding LC filter to PNP circuit

Let's say I want to add a L1C1 filter to power supply of PNP oscillator to avoid a current spikes drained from battery. In case of NPN circuits the designers usually place the L1 to Vcc rail. However, ...
Michal Podmanický's user avatar
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Read optocoupler inputpullup pnp by MCU

I have a switch and want to read digital input pull up state from arduino. how can the key open the pc 817 optocoupler and trigger the pnp gate to read inputpullup pin from digital arduino. That ...
Khales Naim's user avatar
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1 answer
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Light cutoff alarm circuit PNP output

The purpose was to check the voltage on the PNP tr collector side. So when we cut off the light, we expected about 12V. When we detected light, we expected it to be printed around 1.6V. I checked the ...
jji's user avatar
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1 answer
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Why does this NPN transistor conduct current when base is connected to ground?

I have been working on designing a board that contains a seven-segment LED display with red and green LEDs driven by PNP and NPN transistors. The red and green LEDs have different voltages but are ...
Nathan's user avatar
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4 votes
7 answers
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How can I control PNP and NPN transistors together from one pin?

I'm trying to understand how it is possible to control a PNP and a NPN transistor simultaneously from one controlling pin. My issue is that when the INPUT pin is left floating, the transistors drive ...
AKTanara's user avatar
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4 votes
3 answers
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How can I use a PNP transistor as a switch in a 555 bistable circuit?

I am trying to understand how the PNP transistor configuration in this circuit works: It comes from this article: How to build a Simple IR Transmitter and Receiver Circuit using 555 Timer? I believe ...
RickyBoy's user avatar
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1 answer
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How different structure (Resistor, Diode, and Transistor) can be model in IC?

I found this image in the book "Practical Electronics for Inventor". I can partially understand what is happening in diode, and transistor. But how does the resistor works?
cYee's user avatar
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0 answers
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PNP biasing logic resistor configuration

I have a PNP transistor connected as follows. I know that there is voltage divider between Vdd and Vin. What is the logic behind this configuration of PNP? What kind of state it tries to bias it into? ...
lub2354's user avatar
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1 vote
2 answers
104 views

Resistor for open-collector transistor

I have an encoder; the circuit is in the image below: The one that I’m interested in is the PNP one. I want to use a 0-5 V digital voltage, the datasheet says this: Applied voltage: 30 VDC max. ...
Sergio Piccione's user avatar
1 vote
1 answer
119 views

ATmega328P 4-button turn on, auto power off using transistor

I'm trying to create a basic 4-button battery powered remote. The logic behind it is that when one of the buttons is pushed it pulls the base of the PNP low thus turning on power to the circuit. The ...
Gibran Zawahra's user avatar
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What should be the output and purpose of this section of an EV inverter circuit?

What should be the output or purpose of below circuit (which is a part of EV inverter circuit).
rashida mp's user avatar
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1 answer
419 views

PNP: What happens if the base voltage is higher than the emitter voltage?

Can a PNP transistor switch a 5 volt load such that in the off state the base is supplied with 12 volts and the on state is pulled to ground (Vb > Ve)? I remember hearing that the base voltage ...
KJ7LNW's user avatar
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0 answers
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To BJT or not to BJT: That is the question [duplicate]

Practically speaking, when is it better to use a BJT vs a FET for swtiching (not as a linear amp)? Given that FETs have both N-channel and P-channel forms, and BJTs come in NPN or PNP, it seems that ...
KJ7LNW's user avatar
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1 vote
1 answer
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Need help driving the enable pin on a TPS2595 with a voltage divider; not exactly sure which method is better to use

I'm a hobbyist at best, and am trying to overcome the learning curve as far as pull-up and pull-down resistors, N channel transistors and P channel transistors, etc, etc. I've got a USB Type-C charge ...
soconnoriv's user avatar
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0 answers
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Linearize an OTA audio crossfader

I'm working on a voltage-controlled crossfader. The schematic is taken from this thread on the electro-music forum. It's a simplified version of Thomas Henry's VC crossfader. I've been experimenting ...
Triangulor's user avatar
0 votes
1 answer
269 views

Oscillator circuit using PNP transistors

I'm trying to build an oscillator circuit by using PNP transistors, so I would like to know if this circuit make sense, if it will work.
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0 votes
1 answer
144 views

How does this power supply design work?

While looking at a radio unit I was trying to repair, I found a 5V line at 1.2V. I started to reverse-engineer it, but was later able to obtain the schematic: The right side is the input, and ...
Bartek Banachewicz's user avatar
3 votes
1 answer
601 views

PNP current flowing in reverse direction

I though I found an error and it seems that it is not really an error as it works in simulation... I am completely confused and I do not understand how it works. What is the math behind this scheme? ...
Jess's user avatar
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-1 votes
1 answer
201 views

How do I create this circuit using NPN instead of PNP transistors

Due to reasons and curiosity, I want to know if I can recreate this circuit using NPN transistors instead of PNP transistors. I know functionally that they can be the same if we invert the polarities; ...
Wingmore's user avatar
6 votes
3 answers
1k views

Is it possible to make a high-side PNP switch circuit active-low with less than 3 BJTs?

I would like to create a high-side PNP switch. The usual example of the circuit design is active high (on the IO node in my schematic). I figured to invert this, I'...
Nick Bolton's user avatar
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1 vote
1 answer
303 views

Comparator and PNP transistor circuit methods

I need to build a simple comparator circuit. But afraid of some miscalculation in that design. This circuit will use in SMPS, that's why noise can be injected upon components. I choose R1 considering ...
analog_designer's user avatar
1 vote
6 answers
462 views

Should I connect the base of a 5 V high-side PNP to a 3.3 V GPIO IC?

I'm trying to drive a 5V 200mA fan from a PCF8574 powered by 3.3 V. For context, I asked a separate question about using active low vs high on this expander, and @Justme recommended using a high-side ...
Nick Bolton's user avatar
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0 votes
3 answers
70 views

Best way to design a circuit for the following AND logic

I would like to implement the following logic: Whilst the switch S1 is pressed AND there is a voltage on VOLT (this would range from 40-60V) then the output switch would be closed and output would be ...
Hasman404's user avatar
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3 votes
6 answers
159 views

PNP as an inverting sink

I'm using a 74LS137 to drive a 7 segment LED (common anode.) Since it's a sink, it "inverts the demux outputs" as desired: I want to wire-OR two outputs, but you can't do so directly for ...
John H.'s user avatar
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1 vote
0 answers
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Reverse polarity protection circuit consumption

I found this reverse polarity circuit that uses a matched PNP pair and a MOSFET: https://projects-raspberry.com/raspberry-pi-b-power-protection-circuit/ I tested this circuit and with no load i get ...
Geologic's user avatar
1 vote
0 answers
102 views

Not sure about input impedance of this PNP transistor circuit

I have to find the input impedance Zi of the following circuit: Using the small signal equivalent for the transistor, I get the following schematic: It is easy to see, that we need to write the ...
neil_huygens's user avatar
2 votes
2 answers
536 views

Switching PNP transistor by using an opto-isolator

I have a problem with a circuit as shown below. I want to drive a pump with the Pump_enable signal but no metter how is this signal state - high or low, the Q3 and Q2 tranistors are always on and ...
Lime7's user avatar
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2 votes
2 answers
206 views

Dual Comparator Circuit

I've received a board with the following circuit: simulate this circuit – Schematic created using CircuitLab The INPUT is a digital signal coming from a MCU, with HIGH value being 3.3V. Based ...
Fmashehri's user avatar
1 vote
1 answer
140 views

How to stop PNP transistor from triggering at power up

In a simple PNP switch circuit, any capacitance on the base will make the transistor turn on when the 24V (V1) is first applied. It'll stay on until the cap charges. I imagine there will always be ...
Thomas C.'s user avatar
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0 votes
3 answers
283 views

P MOSFET without gate resistor. Why is this not burning up?

I have used this circuit several times and it appears to function as intended, but looking at it I am not sure why it doesn't fail. The intention was for MCU GPIO on the NPN transistor's base to make ...
Feynman137's user avatar
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Faulty PNP Transistor switch fix...what is causing the noise on the base?

I built a ham radio amplifier kit that takes about 5 watts drive and makes 70 watts. It is called a MiniPA70. Here is a website someone put together describing its build/use. http://pa-11019.blogspot....
Jeffrey Edward Messikian's user avatar

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