Bjt Definition and 216 Threads

Hey there, I want to build a simple temperature sensor using a BJT (BC547, 2N2222, or similar). I'm not sure how should I do that. My first thoughts where: measuring the Vbe, using around 9v to 12v as Vcc, the transistor with common-emitter; then just wrap the transistor in plastic or...

I have been checking the BJTs on a car audio amplifier board with my DMM's diode test feature, and I need a little help understanding something I have been noticing: The base to emitter and base to collector voltage drops are present, and show an open circuit when the leads are reversed as they...

I need to know if my formula's are correct for current gain. Sorry for shakey drawing. I know beta would change the dc values slightly but for my prof. it's close enough. Beta AC = 70. DC Analysis VB = R1R2/R1+R2 VE = VB - VBE IE = VE/RE AC Analysis r'e = 25mv/IE Req = R1 || R2 Rout = RC ||...

Homework Statement Homework EquationsThe Attempt at a Solution I have several thoughts about this circuit. My first thought was to decide whether or not the transistor is in active or saturation mode. Assuming active mode operation and neglecting the base current, I see ##V_B ≈ 0V##. So...

Homework Statement Homework EquationsThe Attempt at a Solution I was not too sure about the analysis and thought I would ask some questions. Do I short out the AC source ##v_i## when doing the DC analysis? The input capacitor with ##C = \infty## is designed to couple the AC signal and...

Homework Statement I had a few questions about the npn BJT with regards to designing a few circuits. The questions and my attempts are below. For the calculations, assume ##\beta = 140## and ##V_{BE} = 0.7V## for npn active mode. 1. Fixed bias circuit: Design the resistor values required to...

can you do load line analysis on a bjt with just a knowledge of algebra or is calculus required?

Suppose to have a BJT Common Emitter amplifier like the one below: Now, if we send a signal ##V_{in}## with a frequency belonging to the midband frequency interval, we can consider ##C_1, C_2,## and ##C_E## as short circuit. Questions are: 1) What is the effect of ##C_E## (excluding its role...

Hi! I studied BJT in theory for some time and now I want to use it in practice. What are limitations of BJT in real life? What should I know in order to properly use it (I mean without damaging it) ?

Hi! I was wondering what happens with Base current direction if NPN BJT works in reverse active mode? In forward active and in saturation mode currents are like this: Collector and emitter currents in reverse active mode would be in opposite direction: :

Homework Statement It is required to design the bias circuit as shown in figure for a BJT whose nominal {\beta} is 100. a.) Find the largest ratio {(R_B/R_E)} that will guarantee {I_E} remains within 10% of its nominal value for B as low as 50 and as high as 150. b.) If the resistance ratio...

So, recently I started learning about electronic components and then I started learning about semiconductors. The one which I've been having some real trouble to understand its function is the transistor. So I bought an electronics textbook called El ABC de La Electrónica (The ABC of Electronics...

Hi i have have a small question regrading to a NPN BJT transistor. the DC current gain (beta) is the ratio between Ic/Ib where Ic and Ib are the collector and base currents respectively. Ib is the input current, that's alright , but, i don't get why Ic considered as the output? in NPN BJT...

I would like to know how to design an amplifier similar to the attached circuit with set -3db points, the lower on the order of 10Hz, and the higher on the order of 10kHz. I have designed amplifiers to work with a set gain, but have not dealt with frequency response before. I designed an amp...

i understand this graph the ordering of the regions make sense to me; cutoff: little/no base current ----> no current anywhere active: base current moderately past V_be -----> linear current amplification saturation: etc but here.. http://']http://i.imgur.com/JpGqXUQ.png what is going...

So far the explanation on BJT working principle always explained in electron flow perspective. I felt it's hard to relate with conventional current direction notation when the explanation explained in electron flow direction notation. For example in NPN transistor, the C-E current flow made me...

Hi everyone. I am starting to study transisors at Uni. and I am confuse in some main concepts. i thought about posting it here so someone can help me up. are pi hybrid signals equivalent circuits used with the same porposes as small signals equivalent circuits? or are pi hybrid signals, small...

I would like to know how carriers flow in a bipolar junction transistor when working in saturation mode. Normally, electrons would flow from the emitter to the base. Then, from the base, some recombine with holes nad leave, forming the base current, and the others (the majority) diffuse in the...

so i know that h11 is defined as v1/i1 when v2=0 and so on...but the thing is how do i do it practically...my professor told me that v1,i1,v2,i2 in h parameter equations are instantaneous values of current and voltage of ac in a bjt. he even wrote that to get h11, you have to set v2 of ac=0. but...

Hello, I am reading The Art of Electronics, and I have two specific questions regarding examples it has introduced. I am dealing with bipolar transistors the current chapter. I think my questions mostly stem from not understanding concepts. The text has introduced the technique of...

From the output characteristics of a BJT, it is observable that in the active region, the collector current becomes constant or independent of collector emitter voltage. So, in true terms, it is saturation, then why do we call it the active region? Also, we have the equation:- Ic = (Vcc –...

why are people saying BJTs are cheaper to OPERATE? the field effect devices require less current and should therefore cost less no?

With no external voltage applied there exists an insulating depletion region between all of the junctions of dissimilar materials. This is formed when the dissimilar materials first contact: the free carriers in one material (either positive or negative) diffuse into the second material and...

I have attached the images for the question and the way i attempted it please refer to it and tell me have i made any mistake.I have also attached the image for the solution provided by book, and my answer is not matching to the answer given in the book. Question has asked to calculate the...

Homework Statement VBE=0.7V The transistor in the circuit of Fig. P5.69 has a very high 0. Find the highest value of VB for which the transistor still operates in the active mode. Homework Equations VC>VB IC=IE (since IB is approximated to zero due to high beta) EDIT: IE= [VE-0]/1k (VB -...

Hi! Here is my task: Calculate RC1, RC2, RE2 for maximum undistorted symmetrical signal at output if DC collector currents are IC1=IC2=1mA. Calculate voltage gain Av. Vcc=9V, RE1=1.8kΩ , VBE=0.7V, VCES=0.2V, VT=26mV, beta=100, VA→∞. Solution: RE2=700Ω, RC1=5.724kΩ, RC2=3.141kΩ...

Hyeee. This Gonna Be My First Post. Really Hope You Guys Can Help Me. I Dont Understand On The Operating Principles Of The Sensor Circuit Shown In Figure (d) and Figure (e) . Can Someone Describe It For Me? I Have Quiz On Thisssss..Arghh. Can BJT Transistor Works As Switch? How...

Hi! Here is my task: Calculate voltage gain Av and current gain Ai for circuit on scheme . I don't know how to calculate Ai. I got that Av=-gm*rce*Rc*Rl/(Rc*Rl+rce*(Rc+Rl)) and it matches with solution given in my textbook. I know that Ai=Iout/Iin but which current is Iout? Ai should be...

Hi! Here is my task: Calculate Iout if all BJT's have identical characteristics with β→∞, work on same temperature in forward active mode. Use BJT exponential transfer characteristic. Since β→∞, IB for every BJT should be zero amps and IC=IE. Equation for BJT exponential transfer...

Homework Statement the signal Vsig has a maximum voltage amplitude +-100mv Vcc = 15V, Rc = 2.2khom, Re= 200ohm, β= 100, Vf = 0.7V, Vce,min = 0.2V, VT = 25mV Assume the Capacitor having negligible impedance for the signal’s frequencies. Homework Equations a. Choose the DC biasing...

Homework Statement Hey all, I'm midway through a lab on 'BJT for switching', we are suppose to choose values for RB and RC between a certain range so that it operates in saturation region. I have this circuit: https://dl.dropboxusercontent.com/u/53341615/simulated%20circuit%20step%202.png...

The outcome is: design a single stage amplifier with the following parameters: Rin=1KOhms Rout=1KOhms Voltage Gain=15 corner frequency=300Hz specified Transistor is BC109BP AC supply, 0.5V DC supply 20V supply frequency, not specified, I have assumed 1K We have not been given...

Here is my circuit: β=100, VCEsaturation=0.2V, VBE=0.7V, λ->0, VT=26mV After completing DC analysis I got these results : IB=18.05μA, IC=1.805mA, IE=1.823mA, VCE=4.658V>VCEsaturation=0.2V, gm=0.06943, rCE=∞ Ω, rpi=1.44kΩ. After completing AC analysis I got Av=-115.7, Ai=72.23, Rin=1.040kΩ...

I don't understand why Q1 is on and Q2 is off. Can someone explain me the reason for that? Thanks in advance.

Hi! I want to simulate some circuits with PNP BJTs. I was given voltages VEB=0.7V and VECsaturation=0.2V so my question is how can I modify PNP BJT to use these voltages?

Homework Statement Here is the example along with the solution: What I don't get is what happened to the R_E value. So in this model does it neglect this value? It seems like R_E could be anything and you would still get the same model.I have another question, for this same example, it asks...

Homework Statement We are given that the transistor has β = 30. The BJT is shown below (along with the solution). Every value in the figure is given with the exception of the equation I circled in red: The Attempt at a Solution What I don't get is how they got the inequality Vc - Vb >...

Homework Statement Here is the diagram and solution for the problem: The only problem I have is how the solution was able to find the voltage Vc so fast. They got the answer 3V without showing any work?

So I have a question regarding the gain of common emitter amplifier. Referring to the attached diagram, the voltage gain of the circuit is -RC/RE. However, I don't understand how Vbb can be removed when completing the analysis. I've done the KCL analysis by hand and keep getting a gain function...

This is the result from a lab,but I am not sure the results are correct. Also,when I try to find I(c) , I(b) and I(e),by measured V(RC) and V(RE),I find the results strange. I guess the combination of R1=10k and R2=10k is under linear region,but the dc gain is so small. For combination of...

For BJT single stage amplifier we write gm=Ic/VT where VT is Thermal voltage whose value is 26mv. Now if we have a Darlington pair i.e. two transistor connected in CC-CC mode what will be overall gm. Will the collector current Ic be divided by 52mv or 26mv. (Because in gain equation gm comes)...

Homework Statement The circuit below is a BJT common collector amplifier. Find both the voltage gain (AV = Vout / Vin) and the current gain (AI = Iout/Iin). As with Problem 1, this may seem hard to parse at first, but it is actually pretty straightforward. Carefully replace the BJT symbol...

Homework Statement The circuit below is a BJT common emitter amplifier. Find Vout as a function of Vin. This may seem hard to parse at first, but it is actually pretty straightforward. Carefully replace the BJT symbol with the model for a BJT we used in class, making sure the base (B), emitter...

Homework Statement We have a transistor with RB, RE and A LED being a GaAs Light-emitting Diode (LED with a forward voltage of approximately 1.5V. Values for RB= 2K, Vs-offset=5, Vs-amplitude=4, V-frequency= 1KHz, let β=100 what is the value of the emitter resistor for which the LED...

Homework Statement Why is R_E in parallel with 1/g_m1? I drew the small signal model but it does not make sense to me Homework Equations The Attempt at a Solution

I have a pressure sensor, it has 4 wires, In+ In- Out+ Out-. I excite In+ and In- with a 12V battery and the outputs are about 6V each, the difference is very small, 0.7mV at 1atm and 12.9mV at 100psi. I want to read this with a microprocessor which takes in analog 0-5V so I want to amplify...

i had a thought to stick two diodes together such that the electronic setup was similar to that of a BJT transistor. however i have been told by multiple teachers/professors that the two were not equivalent. I have drawn a picture to show you what i mean. the top two pictures are just the...

How to design a Output enable ckt (like the ones in logic gates and buffers) using a simple component like BJT or FET.

We are studying single transistor amplifiers, and in the text where the collector resistance of the CE amplifier, Ric, is derived, the final equation is Ric = ro[1+gm(Re||r∏)] (approximation) This equation is highlighted and emphasized as something we should remember, then shown again in...

For a common base bjt amp, would I be correct in thinking that to measure total power consumed by the circuit, you would measure voltage from Rc down to Re (inclusive) and take a current measurement from between Vcc and Rc and then multiply together?