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.
640
questions
0
votes
1answer
30 views
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) ...
0
votes
1answer
50 views
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 ...
0
votes
1answer
64 views
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 ...
1
vote
0answers
41 views
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 ...
1
vote
1answer
204 views
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 ...
0
votes
1answer
35 views
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. ...
0
votes
1answer
19 views
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 ...
0
votes
0answers
69 views
Using an NPN transistor as a signal switch
I'm using this NPN switch to turn on and off a clean guitar signal (as part of a much bigger circuit not seen.) The base is connected to the switch, which gives the base 9V through a 1 megaohm ...
1
vote
3answers
107 views
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) ...
4
votes
2answers
158 views
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 ...
3
votes
2answers
122 views
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 ...
0
votes
1answer
68 views
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 ...
0
votes
1answer
61 views
how to tell if this 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 know ?
TEST setup : Supply ...
0
votes
0answers
38 views
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) ?
0
votes
2answers
64 views
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 <<...
0
votes
0answers
41 views
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 ...
1
vote
1answer
71 views
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 ...
0
votes
0answers
41 views
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 ...
0
votes
0answers
36 views
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 ...
1
vote
0answers
54 views
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 ...
-1
votes
1answer
89 views
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 ...
0
votes
0answers
38 views
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 ...
0
votes
3answers
81 views
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 )
...
0
votes
0answers
57 views
Collector Emitter Saturation Voltage
Lately I have been studying the BJT and its respective Transport/Ebers-Moll models with the equations for the Base, Collector and Emitter currents. Assuming an npn transistor, applying a constant ...
1
vote
0answers
44 views
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....
0
votes
2answers
50 views
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 ...
2
votes
3answers
121 views
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 ...
0
votes
1answer
68 views
How to fix this uln2003 circuit?
I am trying to make understand to working of uln2003 but not able to run this circuit properly please anyone help me to understand why this is not working..
1
vote
2answers
61 views
LTSpice RF transistor 2 emitter “the instance has fewer connection terminals than the definition”
I am trying to use the Infineon spice model for BFP640ESD (link for library file), but it has two emitter terminals and I'm not sure how to use it since the BJT models have only 3 terminals and I need ...
1
vote
1answer
70 views
Head to tail transistor pair, not a Darlington pair, not a Szlikai Darlington
I recently reversed engineered a discrete voltage regulator from a board that was performing quite well, and I stumbled upon a weird transistor pair circuit.
simulate this circuit – Schematic ...
1
vote
0answers
64 views
Understanding the VI output characteristic of NPN transistor in the saturation region
I have trouble in understanding the VI graph of the output current (collector current \$I_C\$) in the NPN transistor. More precisely the common base one (this is the first type of transistor I came ...
0
votes
0answers
34 views
Altering PWM on four pin fans using only transistors
I have some high RPM 4 pin Tacho PWM fans, they run at 6000RPM and 56.5 DB at 100% duty cycle the noise is enough to drive you insane - there are seven of them total running off of a SAS backplane, ...
0
votes
1answer
88 views
Constant current limiting circuit
Can someone help me understand the working of this circuit:
My questions :
Please explain me how this circuit will work in its entire operation range.
I am not able to understand the purpose of the ...
0
votes
2answers
140 views
NPN circuit (breadboard)
What does this NPN BJT circuit represent, is it a switch or just a PN diode, and what should this plot look like when we sweep the value of Vbe, and why?
0
votes
1answer
97 views
Can someone explain this part of circuit from BQ500212A?
As the title says, I am struggling to understand what this part of a circuit does. It's part of this evaluation module.
Is there any chance the BSS138 transistors will activate without the SNOOZE/...
0
votes
0answers
37 views
LED Controller Circuit Design with BJT
https://www.circuitlab.com/circuit/mthven79a2m6/led-controller/
I designed a LED controller to turn the led on/off. What do u think about my design?
4
votes
3answers
421 views
2N2222 low side relay switch not turning off
I've been pulling my hair out over this for weeks and I can not for love nor money work out why it's not working.
I have a very standard NPN low side switch setup to turn a relay on/off from a 3.3V ...
1
vote
2answers
75 views
Why does this 8 step sequencer schematic need two resistors for each output pin?
I've found a schematic online for an 8 step sequencer and built it on a breadboard. Before I start experimenting with it and adding features, I'd like to find out if both 10k resistors are needed for ...
2
votes
3answers
68 views
What can I do to get a stable bias on this current sink?
I am still working on trying to get a stable 60 Hz ramp generator with a down-slope, and I am trying to do it from first principles and as simple as possible to understand fully what I'm doing.
I got ...
0
votes
1answer
78 views
Is a resistor compulsory in a NOT gate made from an NPN transistor?
I am making a NOT gate using a BC337/BC547A transistor (tried both) and I have made this circuit (image shown below) using a simulator:
This is working properly. However when I remove the resistor R1,...
1
vote
1answer
111 views
My FM transmitter never works, Why? [duplicate]
I'm trying to build a FM transmitter, but without sucess. The current schematic I'm using is this one:
The alternating current at the (+) of the op amp is the P2 output of my phone.
V3 and V4 are 2 ...
2
votes
1answer
96 views
what kind of transistor is this?
I'm just beginning to understand a bit about transistors and wanted to build my own NOT gate with what i thought was an NPN Transistor. When it didn't work I thought maybe i had the pins mixed up and ...
1
vote
2answers
78 views
How do you get transistor voltage when you only have currents?
β=50 I need to find Vbe and Vce
So obviously it is a NPN transistor, the current is flowing in the same direction so it is in active mode.
Ie=Ic+Ib
1.2mA=1mA+Ib
Ib=0.2mA
Vbe should be around 0.7V for ...
1
vote
0answers
78 views
Can a D667A NPN transistor be replaced with a BD139 NPN transistor in this PSU?
I have a PSU that had a D667A NPN transistor that took some damage. I am not 100% sure what its goal is in the circuit, but I have the impression it is used to drive the power transistor mounted on ...
0
votes
1answer
53 views
NPN Transistor problem
I need to find Vce
Would this be correct way of solving it?
I got 7.551V for Vce
1
vote
2answers
61 views
BCW71 NPN transistor as a switch
I have a simple circuit using an NPN as a switch using the BCW71 (https://www.mouser.es/datasheet/2/308/BCW71-D-1802620.pdf), as seen in the following picture:
My issue is that when I put 3V3 at the ...
1
vote
5answers
1k views
Using a transistor as diode [closed]
What are the advantages of using a transistor as a diode after interconnecting its collector and base?
1
vote
0answers
61 views
How do I connect a NPN transistor so it operates in the saturation region?
I am learning about NPN transistors and I could not find how to connect the transistor so it operates in the saturation region.The circuit that I have made works in the Active region,because when I ...
0
votes
2answers
137 views
Understanding the 2N2222 transistor, Where is this voltage coming from
I was using Proteus to simulate NPN transistor then I saw this
Both Switches are open. Why I see 3.12 Volts
0
votes
2answers
78 views
Common emitter bandwidth and probing
I am trying to design a simple RF amplifier for a 1MHz AM signal (for low-power transmission). My modulator (JFET-based) outputs ~...
