Questions tagged [bjt]
BJT stands for Bipolar Junction Transistor. It is a three-terminal electronic device constructed of doped semiconductor material and may be used in amplifying or switching applications.
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What sort of transistor is this?
I come back to ask for the help of the community in order to identify a device which was given to me several years ago by an electronics component dealer. This time I know something more, precisely
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Taylor expansion relationship with transistor conductivity [closed]
Write an equation that represents the base-emitter voltage change and the collector current change of a bipolar transistor, assuming that the base-emitter voltage has a DC component and an AC ...
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How do I select and use a BJT in a simple LED circuit? [closed]
I am trying to understand how to use a transistor in a simple LED circuit.
The LED (blue) has a forward voltage of 3V, and I'd like to provide it with 19-20mA. VCC on the circuit is 3.3V. I was ...
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The condition of linear operation of the transistor Dipole in small signal mode
How small should the base-emitter voltage changes of the transistor be so that the relationship between the base-emitter voltage changes and the collector current changes can be considered linear?
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I don't understand this temperature controller circuit's behaviour [duplicate]
I am trying to build a circuit to regulate temperature for a few microheaters. Here's the circuit I am using:
This is a constant temperature controller circuit often found in the research papers and ...
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BJT Amplifier simulated gain is only around 80% of calculated gain. Why is this and how to improve calculation vs simulation accuracy?
I'm trying to design a CE BJT amplifier in Multisim with 100mVp 1kHz input, and target gain of around -208.8. Starting from my choice of Vcc = 50V and Ic(DC) = 15mA, here is the design I came up with:
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How does this BJT monostable one-shot work?
This circuit comes from Hamilton's Handbook of Linear Integrated Electronics for Research, 1977, p. 240. It is similar to the common BJT monostable multivibrator, but it doesn't include the feedback ...
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BJT ring oscillator
I would like to build a ring oscillator with a BJT but the waveforms do not look correct. currently, I am using the following circuit:
My question is how do I control the frequency while at the same ...
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Current source using bjt current mirror [closed]
I have built a Current source of 1ma using the bjt current mirror. Whats the maximum and minimum values of load resistance that can be connected to it?Neglect Early voltage effect .
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Amplifier/ tone control [closed]
how to make an amplifier using BJT with bass, mid, treble parts
with this spesification
• Bass : cut off frequency pada 300 Hz
• Mid : Center di 1 kHz
• Treble : cut off frequency pada 10 ...
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Operating regions of BJT
My TB says in saturation mode, the base-emitter and collector-base junctions of BJT are forward biased and in cut-off mode both junctions are reverse biased.
But in this graph the saturation region ...
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How to read BJT output characteristic
What's the propper way to read current graph / output characteristic of BJT?
Is it useful if there is no DC load line plotted?
I'm very beginner and I thought that only possible operating points lay ...
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Behavior of BJT collector current in saturation [closed]
Let's assume that we have NPN BJT with absolute maximum rating of collector current = 1A.
Let's assume that we have separate power supplies for base-emitter and collector-emitter.
The collector-...
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Difference between IGBT and FET+BJT
What are the practical differences between a true IGBT and a combination of FET and BJT, apart from a more efficient production and packaging? Can I obtain a device of comparable qualities to IGBT if ...
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Confusion with a BJT datasheet
I'm designing an amplifier with a BJT and I decided to use the FMMT495TA (https://www.mouser.es/datasheet/2/115/DIOD_S_A0002833682_1-2542044.pdf) as there will be 0.5A going through the collector. Now,...
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Drive Power LED with a BJT
I'm studying how the transistor works as inverter but in some books they have a small section where they talk about how to drive lamps and LEDs, but they don't use the same configuration. I would like ...
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Why am I getting heavy output distortion from a BJT amplifier when driving an 8 ohm load?
Hello electronics professionals and enthusiasts! Software engineer mingling with breadboards and discrete components in his spare time here.
I'm trying to build a simple BJT amplifier for my electric ...
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How to design BJT common collector amplifier?
I am working on a school project and I am struggling to design what is supposed to be an easy CC-amplifier. All other parts of the circuit are calculated and should work. The power amplifier is what's ...
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How can I eliminate cut-off [closed]
I have built a multistage bjt circuit. I got my gain to be around 40, but I cannot figure out how to eliminate the cut-off. The only values I can change are the resistor values (except the 50kOhm ...
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Why is the collector swing greater than the power-supply voltage?
My Vcc = 12v and the voltage peak across the collector current is 1.46kV. why?
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op amp positive feedback Schmitt trigger
I have recently come across the op amp Schmitt trigger presented in 3rd edition art of electronics. I decided to build the circuit myself in circuit lab, and I have some questions regarding its ...
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Drawbacks of Class A push pull audio power amplifier?
I am willing to develop an Audio power Amplifier myself in a Push Pull configuration of two complementary transistors (NPN,PNP).
On the internet, it is found that most of the conventional Class AB ...
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Vintage Intercom BJT Preamplifier: Purpose of Capacitors and DC Bias Troubleshooting
EDIT - Further Research - Comments on Common Emitter Preamplifier
https://sites.google.com/a/davidmorrin.com/www/home/trouble/transistors/amplifiers
The preamplifier stage in the circuit below has ...
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If I want to limit the bandwidth of this BJT to 10 kHz, what resistance should I consider when need to calculate the value of capacitor Cf?
My wish is to get the capacitance value by calculating R when I use the hybrid-pi model, so use the formula Cf = 1 / (2 * pi * f * R).
I would like to ask if the R value needed to use in the above ...
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Output characteristics of a BJT
While plotting the output characteristics of a CE configuration, the graph between VCE and IC, it shows that when VCE=0,IC=0 My doubt is whether VCE=0 means we are shorting collector and emitter or ...
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Level shifting from 3.3 V to 1.8 V at 500 MHz
How can I translate a unidirectional signal from 3.3 V to 1.8 V with a bandwidth of 500 MHz?
The signal I am interested in is the output of a high speed comparator (TLV3601) and I have to measure the ...
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How should I approach the circuit analysis of this reflexive receiver? [closed]
I built the following circuit:
I got this circuit from this YouTube video.
It works well, although the volume is quite low. My main question is how would I approach circuit analysis of this circuit ...
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How can I solve this circuit with two BJTs?
I am analyzing the circuit in the picture attached. It's a connection with two BJTs biased slightly different, both having the same load.
The struggle I have here is that any method of calculation I ...
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Single stage common emitter amplifier output voltage
I am having trouble getting the voltage Vout=1.25v and the gain should be Av=5 and I have the input voltage Vin = 0.25v. This is my schematic, what did I go wrong?
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Strange low frequency sawtooth in a 110 kHz Hartley oscillator
I am trying to build a Hartley oscillator for 110 kHz using a BJT according to the following schematic:
I am assuming \$ \beta=100\$ and \$ V_t=25mV \$
The collector current is about 1.63 mA, Vc is ...
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STM32 12V input via NPN transistor
I'm trying to sense a 12V input on a STM32 microcontroller.
This is the schematic I came up with:
When I short the pins of CN1 the STM pin goes LOW and I can read correctly that there is an input.
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Multistage common-emitter 2N4401 amplifier
I am trying to design a common-emitter multistage amplifier with gain 40 given \$V_s(t)=0.25\sin(2\pi 1000t)\$ and \$V_o(t)=-10\sin(2\pi 1000t)\$. Vcc is 24v and I want my q-point to be Vce=12v. I ...
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Output voltage of BJT shunt regulator in terms of input voltage
I am working through a tutorial to prepare for a test tomorrow and am completely stumped with a step in the algebra.
The question is in the image below
I am trying to complete b).
I have understood ...
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Is it possible to use a BJT as a switch if I have a pull-up resistor of 200k at the collector tied to 0.8V?
I have a controller which has an active low input and an internal pull-up resistance of 200k tied 0.8V. I would like to use a BJT as a switch for the microcontroller to control the controller input. ...
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NPN BJT + P-Channel MOSFET relay circuit
Bit of a newbie here, does this look as if it will function correctly? I want to use it as a relay-type circuit to use a 3.3V from a MCU pinout to send 12 V over the load, but the results are looking ...
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Current limiting circuit: Need for replacing the pass transistor with MOSFET?
The article says "The circuit provides an approximate constant current at high voltages, but it doesn’t enter regulation until it reaches nearly 60V due to the base current the transistor ...
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BJT transistor sum
Here I considered it is in active region and considered Vbe=0.6 V.
I did this:
I considered it is in active region but it Vce is less than 0.2 V.
What should I do next?
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Why does current mirror need a diode connected configuration?
I am not able to understand why the connection between gate and drain of the first MOS is required.
A similar question to this is asked here but it is BJT based current mirror and the answer is there ...
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VBE of BJT keeps increasing beyond 0.7V, Why is it not getting saturated around 0.7V?
Background: I am trying to understand the progressive steps to the final current limiter mentioned in this site.
As a first step, I am checking the effect without the feedback loop:
Why is the VBE ...
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Stage of Amplification In BJT [closed]
For a common emitter current amplifier, at what point, stage, or junction does is applied current amplified?
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Is this IC a BJT?
I have a unknown 3 terminal IC in a SOT23 style package. I think it may be a BJT but I am a bit puzzled by the results of probing a DMM across all the terminals in diode mode. Below is a figure of the ...
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Same collector current of BJT simulation
How do we simulate 2 bipolar junction transistors of the same collector current in LTspice which has different emitter base junction areas?
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Base resistor R2 for voltage bias [closed]
Can someone please explain to me how they arrived at 38.8k ohms for the R2 from this site, under the voltage divider bias technique... I just can't seem to figure it out. Pls help out voltage divider ...
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Common-Emitter Amplifier
I have the following common emitter amplifier circuit.
I am also told that, when taking the specs above,to consider a 20% safety margin to accommodate for possible parameter variability.
Then there ...
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How noisy is a saturated PNP BJT as a switch compared to a p-channel enhancement mode MOSFET?
I want to switch on phantom power (12V through 680ohm) electronically in order to guarantee simultaneous delivery and not have the comparatively low resistors load the input in case phantom power is ...
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Formula for R1 and R2 of a voltage divider bias
Please I'm asking if the stated procedure for R1 and R2 of a voltage divider is correct i.e if its valid way to come up with their respective values. If so, how do interpret the two statements ...
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Load current of a transistors (BJT)
What does the load current of the transistor (BJT) mean? Please explain.
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NPN Transistor calculation
I want to find the value for \$R_1\$ and \$R_2\$. Is my calculation right? Assume \$h_{fe} = 120\$, \$V_{ce} = 25\$.
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Darlington configuration using BJTs [closed]
Does a Darlington configuration using two BJTs, say a BC548, override the total power they could dissipate?
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Why would this circuit have a "maximum" output power?
For the circuit above, in addition to what's labeled, the Zener voltage is given as Vz = 4.7V, and we have that 11.5V < Vin < 13.5V. Now, as long as the op amp is not saturated, and the Zener ...
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