A bipolar junction transistor (BJT) is a type of transistor that uses both electrons and electron holes as charge carriers. In contrast, a unipolar transistor, such as a field-effect transistor, uses only one kind of charge carrier. A bipolar transistor allows a small current injected at one of its terminals to control a much larger current flowing between two other terminals, making the device capable of amplification or switching.
BJTs use two junctions between two semiconductor types, n-type and p-type, which are regions in a single crystal of material. The junctions can be made in several different ways, such as changing the doping of the semiconductor material as it is grown, by depositing metal pellets to form alloy junctions, or by such methods as diffusion of n-type and p-type doping substances into the crystal. The superior predictability and performance of junction transistors soon displaced the original point-contact transistor. Diffused transistors, along with other components, are elements of integrated circuits for analog and digital functions. Hundreds of bipolar junction transistors can be made in one circuit at very low cost.
Bipolar transistor integrated circuits were the main active devices of a generation of mainframe and mini computers, but most computer systems now use integrated circuits relying on field effect transistors. Bipolar transistors are still used for amplification of signals, switching, and in digital circuits. Specialized types are used for high voltage switches, for radio-frequency amplifiers, or for switching heavy currents.
Hello!
I am having trouble with this emitter circuit.
I am given U0 as well as all of the resistor values and I need to calculate the following.
## I_c## ##U_{CE} ## ## U_{C} ## ## U_{a} ## ##U_{Ca}## ##U _{Re} ## Now important to note that all of these need to be calculated at the working...
The diagram of the BJT amplifier small signal model is below. This is not really a homework question as I am self-learning electronics, but I was advised it may be better placed here than in the technical portion of the forum. Thus I do not have an "attempt" at a solution (which is given as RI...
THIS IS NOT HOMEWORK
I design audiophile power amps as hobby. I need to match power transistors. It is A LOT HARDER than I thought. I built a test fixture to hold up to 50 transistors at a time. I try to match sets of 13 to about 1mV which is very tight as Vbe change is about -2mV/deg C. I have...
Hello,
I need help with this bjt transistor and finding the Q point. The problem I have is that I don't know how to do the thevenin theorem on this one. If someone could help me and show me how its done that would be great. Thank you!
The transistor looks like this on the picture:
This is my...
Summary:: So apparently the equations schould be correct but I am not sure about it.
Isnt R1 = Ub(10V) - Base voltage / Iq + Ib --> Ub is the source voltage 10V.
And schouldnt R2 be :base voltage / Iq?
I have been studying Studying Donald Neamen's Electronic Circuits 4th edition and Sedra Smith's Microelectronics 7th edition for quite some time now. I have been self studying. After searching extensively on Internet as well as trying to understand from the books, I have not been able to...
Hi i got a question ,how do i calculate the input resistance ,of the RS resistor ,so i would get half of the voltage of the voltage source (500mA) .I've created the circuit in ltspice and found out that its around 95K ohms to get 250mA,but how would i calculate it .
Ive also attached my...
This is a BJT common collector colpitts oscillator.I have found how to find the feedback fraction from this site:http://fourier.eng.hmc.edu/e84/lectures/ch4/node12.html but I have searched for hours and haven't found the amplifier gain of this circuit.
I have found the amplifier gain for...
I can't find the formula for the current flowing from the base to the collector in saturation mode of BJT.Any help?There are many references to the emitter current in the forward active mode but none for the base-collector current in saturation mode.Help appreciated.
Assume we have a common collector circuit with a emitter resistance of 1k Ohms.Vc = 10V Ve is connected to ground.
Now we connect the base of the transistor to 5V . The base current will be 5-VBE/1000 Amp.Let's say a voltage drop of 0.7 in the BE junction .We will get Ib = 4.3mA.
Ic = bxIb =...
If I have an NPN transistor and let's say we set the base voltage higher than the collector voltage.(Emitter is connected to GND).There are 2 currents flowing in the base because we have two forward biased junctions inside the diode , 1 is the current flowing from emitter to base and 1 is the...
##V_{BE}## is basically the difference in voltage between the base terminal and the emitter terminal.
Normally when silicon is used and the transistor is biased to operate in the active region, ##V_{BE}## = 0.7 V approximately.
The way I understand this is that for an npn BJT, the applied...
I am trying to create a receiver for a personal project I am working on. This is the RF amplifier that I was given by a book I am following. How does this circuit work? Usually for a BJT amplifier I find the DC bias point and then use the small signal model after I bias the circuit? I understand...
I am given that all the BJTs are the same.
First of all, when finding node voltages like Vref should I make the node voltage a voltage source first and then do circuit analysis? If so then I would use KVL but that does not give me Vref = 2Vbe.
I do know that Vref = Vb1 = Vb2. What am I doing...
I’ve attached an image below of a section from my textbook and some circuit simulations. The textbook gives an equation for the collector current in a bjt transistor. The simulation shows two circuits (with the same bjt transistor) that hav equal values for all variables present in the textbook...
I am looking for small signal BJT that has very low leakage current when the base is biased at about 0.2V. I have issue of transistors drawing collector current when the base is at about 0.25V that is way less than the normal turn on of 0.6V to 0.7V. I am currently using BC546 or 556, and KSA992...
Hi,
before you proceed with reading this question, I would like you to know what I do not expect anyone to solve this task for me. I have a problem with a single step in the solution and I'm only asking you to help me with this one step.
1. Homework Statement
Compute ##R_B## so that Q-point of...
Homework Statement
I'm studying a circuit with BJT's and I'm asked to determine the input resistances of the two amplification steps of the circuit. The circuit I'm analyzing is the following one:
Homework Equations
3. The Attempt at a Solution [/B]
To determine the input resistances I...
Homework Statement
[/B]Homework Equations
For 1st I think answer is B
For second I(c) = B I(b)
B is beta
The Attempt at a Solution
For 1st I think it's B
But book says answer is D
Is book wrong?
For second I'm getting:
I(c) = 3mA
And beta = 200
So I(c) = B I(b)
3mA = 200 I(b)
This gives I(b)...
Hey guys, I'm confused as to the difference between the h-parameters usually given by datasheets and their hybrid-pi model analogues. For instance, I know hfe = Beta in small signal analysis, but what about the other h-parameters.
Thanks for any help with clarifying this.
Hey everyone,
I'm trying to plot a straight line for a bipolar junction transistor to find the room temperature, T, using my experimental results for the associated base-emitter voltage, ##{V}_{BE}## and collector current, ##I_C##. Here's the equation that I'm using:
$$ I_C = α_F {I}_{EO}...
Homework Statement
Homework Equations
KVL
The Attempt at a Solution
Using KVL around BE loop
0-0.6-i_e*(30*10^3)-15=0
i_e=-0.52mA
However, I stuck when I tried to find i_c and use KVL around CE loop/ CB loop
For CE loop:
10-i_c*(15*10^3)-Vce-i_e*(30*10^3)-15=0
For CB loop...
This is what I have and I was wondering where C2 might go if I make apply the hybrid pi model on this circuit. I know that all the DC Voltages should be shorted if I were to make use of an equivalent circuit, so that in the hybrid pi model R1 should be in the input and R3 in the output. But what...
Homework Statement
Does this mean that the forward bias p-n junction starts behaving as a conductor at very small input voltage i.e. of the order of 50 mV and it decreases as VCB increases?
The two circuits i.e. forward bias circuit and reverse bias circuit are independent. Then why should...
Homework Statement
see pic in the attachment
beta = 100
Homework Equations
Rinput=Rth
Vinput=VTH
iB= ic/beta
IE=ic /alpha
iB=iE/(beta+1)
gm=IC/VT
Avo=-gmRC
Av=-gm(RC||RL)
Gv=-Beta[(RC||RL)/Rsig+(beta+1)re
re=alpha/gm
The Attempt at a Solution
solving each stage separately. First DC analysis...
How am I supposed to calculate ohmic resistance from a non-linear electronic device component?
Say, for example, I need to calculate ohmic resistance of a pn junction of bipolar junction transistor from its forward I-V characteristics curves. (It can be either Base-Emitter junction or...
For the B) part, I don't get why is it that for calculating voltage between collector an the emitter (Vce) I take into account diode on base (0.7V), whereas for part A) it's ignored?
Why is Vce in part A and part B are calculated differently? Why is it that in part A voltage of 0.7V isn't taken...
Homework Statement
I have been given the world's longest transistor problem as an assignment :wink: Here is the circuit:
I am asked to find:
a) V1, V2 and V3 using DC analysis
b) AC equivalent circuit
c) AC tension gain: Ava=Vx/Vsig
d) AC tension gain: Avb=Vo/Vx
e) Total AC tension gain...
Homework Statement
For beta = 100 and assuming ro is very large, what is the DC voltage at the collector?
Homework Equations
IB = IE(β+1)
IC = β*IB
The Attempt at a Solution
Since IE = 0.5mA, IB = 0.0505 A
Then, IC = 5.05 A (which doesn't feel right)
VC is the same potential across the 30kΩ...
Homework Statement
Homework Equations
KVL
The Attempt at a Solution
This is the solution given:
VB = (VCC*30k)/(70k+30k) = 3V
Why is a voltage divider being used to find Vb?
{Moderator note: moved from technical forums, so no template}
Hi,
My mid-term quiz is next week. I have tried to solve this question but I'm stuck on Qn 4 Part H. Any hints??
Image for Qn 4:
http://imgur.com/gb9jEfW
My Answers for QN 4:
http://imgur.com/a/fS3GM
Can you help me check my...
Recently I started studying semiconductors and analogue electronics. First I studied the diode and its I-V characteristics and analysis in DC circuits, as well as in AC circuits.
Now I started with BJT transistors. I was explained that transistors act as electronic switches. My problem is not...
I don't know how to calculate the voltages at the bases of every transistor shown in the lower row of that picture (~3V (2.9..V), ~2V, ~1.8V). Any help would be appreciated! - I'm currently trying to figure that out...
The other thing I don't really understand: Why do the transistors in the...
Hi,
In my electronics class we are learning BJT, Mosfet, JFET theory. My gripe at the moment is that when teaching this you are taught how to troubleshoot and solve for circuits already made. This means you are always solving for various voltages, currents, Gm etc etc. With no previous...
Homework Statement
Analyse the circuit to provide predictions for (a) the differential input resistance, (b) differential voltage gain, (c) single-ended voltage gain, (d) common-mode voltage gain, (e) common-mode rejection ratio (CMRR) in dB, (f) common-mode input resistance and (g) the...
I am reading The Art Of Electronics, and I realize this is more of an encyclopedia rather than a textbook. I have referenced other sources as this has mainly served as a compass for me to learn about each subject area.
My question is fairly simple and straightforward. I'm using multisim to...
<< Obnoxious all caps post fixed by Moderators >>
I have made an audio amplifier using an LM386 IC, but it does not amplify any sound from the microphone. Please help me to improve this using a Darlington pair or any other power transistor like the TIP147/142...
Hello people,
I am working on a BJT NPN amplifier the model that I've choosen is 2N2222 : http://www.e-voron.dp.ua/files/pdf/tranzistor/2N2222.pdf
I am having 3 problems here:
1) am not having any AC voltage at output Vce seems like I have set wrong operating point?
2) I am trying to figure...
I need help in making my project using Bipolar junction transistor. I'm Engineering student (Ist year). Can someone here suggest me a Funtastic project that i can make easily and impress my teachers as well using BJT transistor. I have rea the Cascade, cascode and Darlington technique to amplify...
Homework Statement
This is not a homework question. I am trying to learn how BJT work as a switch so I come out with circuit to understand how BJT functions as a switch. I use mulitsim by the way to try out these circuit
2. Relevant diagram
The Attempt at a Solution
[/B]
I understand that...
Please help how Ve is calculated what i think is that it should be:
-Ve=-Vee+IeRe;
How Ve is taken positive please someone draw equivalent circuit for same
Homework Statement
In my book ,I found this line which says ,"The collector current comprises two components-the majority and the minority carriers .The minority-current component is called the leakage current and is given the symbol ##I_{CO}## .The collector current, therefore is determined in...
Homework Statement
1. Given the above circuit, derive an exact equation for ##I_{out}## in terms of ##I_{REF}, V_{BE1}, V_{BE2}, \beta_1, \beta_2, R_{E1}, R_{E2}## and ##V_{CC}##. Do not make any assumptions.
2. Simplify the equation from part 1 by assuming ##V_{BE1} = V_{BE2}## and that...
Homework Statement
Hi everyone, this is not homework, but I can't seem to see something.
I have a multiple BJT circuit I've drawn, and I want to analyze it:
Homework EquationsThe Attempt at a Solution
Assume the transistor ##\beta##s are equal for both transistors and are known. Assume...
In BJT hybrid pi small signal model, we have a resistor "ro" between Collector and Emitter.
This resistor is to include the change in collector current when there is a small signal voltage change between collector and emitter. (due to early effect)
I am finding that all BJT hybrid small...
I'm having the worst time ever with a two stage cascode bjt amp. See attached circuit image. In the circuit photo the "In R: 168ohm" is the amps input resistance according to LtSpice. I usually have luck with LtSpice. The circuit shows real measured resistor values. I built a LtSpice version...
Homework Statement
hello, i need to design analog circuit that has a transfer curve as seen in the following image using resistors, capacitors,voltage, and BJT (with beta value of 100).
the parameters are:
A=75
f1= 21Hz
f2=21 KHz
M1=40
M2=-20
the circuit also need to have input resistance of...