Questions tagged [npn]
A type of bipolar transistor comprised of n-type semiconductor in contact with p-type semiconductor which in turn is in contact with a n-type semiconductor -> thus NPN. 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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Large signal model analysis of npn BJT
I have the following circuit and I am trying to find VB, VE, and VC, and consequently IB & IC. The "hints" I am given are (1) to assume that vs has a DC value of 0V, (2) to use the large-...
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What is the point of the diode in parallel to the fan here?
Sorry - no background in EE so this might be a bit of stupid question.
I'm looking at this simple circuit and am trying to understand the point of the 14N007 diode that is put in parallel to the fan ...
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How to control transistor with lower base voltage than supply voltage
Here is the link to simulation of h bridge that I built Simulation link in this I was somehow able to control transistors with 5 volts when supply was 9 volts
but I still didn't completely understand ...
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Unclear about fluctuating frequency when using NPN transistor
I am trying to build a more complex circuit but am having trouble starting off. I am using tone() to generate a frequency on my 5V Arduino Nano on D3. If I measure the frequency directly at D3 to GND, ...
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What are the resistor values that I should use in order to get 38dB gain? [closed]
I have build a common emitter-common collector multistage BJT amplifier.
I want to get an output gain of 38 dB under the conditions of 8 ohms load resistance, 6 volts, 25 mVpp input voltage signal. ...
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Irregular common emitter amplifier design
Would anyone know of any merits (or demerits) to the common emitter amplifier represented in Figure 1 in comparison to one of a regular pattern (Figure 2)? Thanks.
(The 'DS548' transistor in Figure 1 ...
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Activate 12 V Relay with a 5 V GPIO
What is the reason of using 10 kΩ resistor in series to the control signal? Is it related to the base current according to the NPN transistor's datasheet?
For example:
My CONTROL/GPIO is 5 V.
The ...
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Confusion about when to use B*Ib = Ic vs the voltage diode equation for transistors to obtain Ic
When we have an NPN transistor in forward active mode, why do we sometimes use this equation to find the collector current I_c (whereby V_be would be the voltage across the base emitter junction)?
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How can I increase the base-emitter voltage of an NPN transistor in forward active region?
For a project which involves amplification, I think I have to increase the base voltage, keeping the emitter voltage the same so that my circuit will not go out of forward active region as the ...
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NPN transistor switch with load at emitter pin
I found a schematic with a 55 timer driving two transistors, each of which switches an LED (see below).
When the 555 output is low, LED1 is OFF and LED2 is ON.
When the 555 output is high, LED1 is ON ...
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How to convert NPN transistor to PNP transistor? [duplicate]
I am making a circuit using a 4 pin hall sensor with arduino. It turns out that the hall sensor outputs a negative voltage as output, which arduino cannot read, so I will need a PNP transistor, I don'...
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What happens when input current in common base amplifier circuit is increased?
Looking at the equations of the common base amplifier circuit shown below:
The input current 𝐼𝑒 should be given by the equation: $$I_e = (V_{in} - 0.7)/R_e$$
Then, the output current 𝐼𝑐 should be:...
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Why does this transistor limit the current so much?
I have been trying to understand how a transistor works. I bought a simulator to be able to understand it better.
Below is a small circuit I designed. The load is a lamp. The characteristics of the ...
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How do i control a 6 V supply output based on a 5 V input?
I have a signal from a microcontroller that varies from 0 V to 5 V. I also have a separate 6 V supply to power a motor. I'm trying to design a circuit that allows the microcontroller signal to ...
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Two BJTs together
simulate this circuit – Schematic created using CircuitLab
So the BJT's B-E diode is turned on with 0.7V, and beta in active mode is 100 and beta in saturation mode is 10. I'm trying to find ...
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Water detector with a BC547 and help understanding transistors
I have set up a basic water detection sensor using a BC547 transistor to switch on an LED if there is current between two electrodes (which are spaced about 1 cm apart):
I'm trying to understand more ...
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Transistor turns off only after a delay
I'm building an IC programmer (for the AS5043 sensor) that requires two voltage levels; 5V and 7.5V. I decided to control those with two PNP transistors. I'm controlling them from a 5V microcontroller....
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How to design a square wave inverter circuit without an op amp
I am using an NE555 timer circuit to generate a 0 to 12 volt 10kHz square wave.
I would like to invert that square wave (so inverted signal is 0 when original is 12V and 12V when the original is 0 V.)
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Common base question
I'm trying to solve this problem where I find Vout/Vin if rπ if infinite. I also have to conside early effect. When I try to solve it, I get Vπ = 0 and that makes gm zero, a bit confused on that.
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How to choose the correct transistor?
I am having trouble understanding the definitions for the transistor.
I am checking many different transistors and unfortunately every company has different words/symbols.
For example, in one company'...
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2N2222 NPN Transistor, no current flowing through collector
I have a 2N2222 NPN Transistor wired up in the most basic common emitter setting (emitter grounded, base hooked up with a 1k resistor to 5V, collector connected to load and load connected to +12V). ...
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NPN Transistor Data Sheet, Source vs. Sink Current
Even though I'm an EE with 30+ years experience, a simple question asked by a junior colleague really stumped me. Namely, on a data sheet (e.g., for a 2N2222), that transistor can only SINK ...
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Question about diode connected transistor (BJT) with current source
I'm trying to find ΔV for this circuit, but I'm having a bit of trouble doing so. I think the current on the right BJT will be n times greater than the left, but I'm not sure about that either. It ...
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NPN transistor turning on with grounded base
The NPN transistor in bottom left with grounded base is turning on in circuit simulator for some reason.
Can someone tell me why is this happening?
Circuit Simulation link
I know why the other 3 ...
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H bridge with a single I/O control and NPN at the top
I want to control a 4V motor to rotate both directions which draws 100mA and I was looking at the H-bridge schematics. The tutorial says that you should place NPN transistors at the bottom if you need ...
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Fast voltage regulator for output of an function generator
First, I am not an expert in the electrical field:)
In a real-time control system (in LabVIEW), for actuating a piezoelectric, I use the generated signal (sine signal 20khz and 10<V<100 Vpp) ...
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Calculate base current NPN high side transistor
Say I have this configuration:
simulate this circuit – Schematic created using CircuitLab
I want to calculate the current going to the base of the NPN transistor.
Specifically for PMBT3904,215 ...
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Why must the p type be connected to the power source, and the n type be connected to ground? [closed]
When we have mosfet transistors, why must the p-type be connected to the power source, and the n -type be connected to ground? I don't see what will go wrong if we do it the other way. But a book I am ...
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What is the (typical) value of SPICE parameter ISS for a (vertical) npn transistor?
SPICE gives a default value for the (collector) substrate leakage saturation current ISS. The default is ISS=0 but I would like to know the real value for an integrated vertical npn transistor. The ...
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Where did the base get the current from?
Still learning on my own so I am really not an expert.
I built a small circuit and can’t get the expected behavior.
Here is the schematic:
This is pretty simple. The PNP on top is connected to 5V on ...
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Negative differential resistance on current sink
Let's assume we have this circuit:
simulate this circuit – Schematic created using CircuitLab
I was looking in creating a costant current sink but I have found something very interesting. ...
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Interpreting the state of the transistor
In this scenario, let's say that XMM2 has a reading of 0 A and XMM3, being a voltmeter, has a reading of ten volts.
I presume that XMM2 reads the base current, so since there is no IB, there will also ...
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Transistor how to turn lamp on/off
I am trying to design a very simple schematic and trying to understand how the transistor works as switch.
Transistor: Datasheet
Description: NPN - Pre-Biased 100mA 50V 100mW USM(SC-70-3) ...
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Shorting NPN transistor base to ground
What is the normal convention(safe and reliable), should one connect NPN transistor base to ground or should a resistor be used?
My logic tells me that in common emitter mode, shorting base to ground ...
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When using an open-drain output to drive an NPN transistor, can the base resistor be replaced by a pull-up?
Assuming the value of R1 is the correct value for the base resistor for the given motor L1, is it okay to omit the additional base resistor, used in push-pull applications, for an open-collector ...
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switching shape memory valves with microcontroller using NPN transistors
I am using a standard NPN transistor-as-a-switch set-up to use a Teensy 4.0 to switch a bunch of shape memory valves (valves controlled by a wire that changes shape when heated by a current). I have ...
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How to tell if a proximity sensor is NPN or PNP?
I have a proximity sensor without nameplate. I have done some tests that made me think it is a PNP (normally open).
Is my assumption correct? Is there another method to find out?
Test setup:
Supply ...
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Load resistance of this circuit
I want to make sure I understood this correctly .
If I want to measure the load resistance of this circuit, is it between (A - G) ?
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Transistor: Getting “incorrect” graph for input voltage to output voltage
I tried drawing the graph of \$v_o\$ vs \$v_i\$ for a bipolar junction transistor. I used the below setup (common emitter:)
By design of how the base is a small part compared to others, \$I_b <<...
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Two PNP Transistors - Jumper Collectors with Emitters and Bases at Same Potential?
In the attached image, OUT1 and OUT2 are logically identical (provided for redundancy).
I'm wondering if it's valid for OUT1 and OUT2 to be tied together and brought across a single load? This is ...
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Driving lamps with the fewest number of NPN switch transistors
I'm building a small system to drive some Nixie lamps and I'm missing some of the classic ICs that could make this design significant simpler. I ended up with some discrete NPNs to select the lamp and ...
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Problem in 5v pump
I connected the pump to tip122 darlington transistor to control it via serial port.
but the pump doesn't work. instead , it makes sound.
how can i make the pump work
the circuit of the tip122 :
the ...
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Help solving thermal runaway in voltage follower circuit
I'm trying to build a circuit to drive a heating element. In testing a portion of the circuit, I've noticed what looks like some kind of thermal runaway in the Darlington transistor I'm using, but I'm ...
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LTSpice BJT Model Help
I am new to LTSpice and I was trying to make some experiments with BJTs. In particular i was trying to model a npn with VbeON = 2V. From the the ltspice site i found that the built in potential of the ...
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NPN transistors as a switch with an Arduino
I'm trying to use 2 NPN transistors as a switch as shown in image-1.
When I connect pins 4 and 5 of the Arduino to the base of each transistor it works fine, but when I try connecting pin 5 to the ...
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NPN BJT common emitter amplifier input impedance
I am trying to find the input impedance of this circuit.
In this circuit 10K resistor is load.
I looked at my book but could not find any circuit looking like this because none of them has C1 ...
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BJT Constant Current Driver
I'm currently working on this circuit and I ran into 2 questions that I'm not sure I understood them correctly ( I have U1 = 15V , URE = 2 V , β = 180 , UCE = 5V and a constant current I = 2mA )
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Transistor is OFF but the voltage at the emitter is the same as voltage at the collector
This is simple simulation below of an NPN transistor:
In the above transistor, without giving any base voltage, whatever voltage I give at the collector of the transistor, I am getting at the emitter....
user220456
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Best way to AND all connected inputs to one output
I have an CNC router with 7 x SN04-NPN sensors connected in parallel with one control board input. The problem is obvious, i got random false endstop triggers due leaking of SN04. I know i should have ...
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Transistor in cutoff mode but still allows current to flow
Hello everyone,
I am a freshman in computer science, and as we are dealing with a lot of hardware, we stumbled upon transistors. We learned that if a transistor is in cutoff mode, it basically acts as ...
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