Bjt Definition and 216 Threads

Homework Statement The circuit in the figure has the form of a BJT inverter, but also has a resistor connected between the emitter lead and ground. This addition provides feedback between the output loop of the circuit and its input loop. (a) Find an exact expression for the Vin-Vout...

Homework Statement The terminal voltages to ground are measured on a particular BJT. In what region does the device operate if these terminal voltages are equal to the following values: a) Vc = 6V, Vb = 0.6V, Ve = 0V b) Vc = 6V, Vb = 2V, Ve = 1.4V c) Vc = 6V, Vb = 6V, Ve = 5.4V d) Vc =...

I'm trying to understand the differential mode for a BJT. For the second picture, when we apply +1V to the base of Q1 and 0V to the base of Q2. Why is the emitter voltage .3V instead of -.7V? Similarity, for the third picture, why is the emitter voltage -.7V instead of 1.7V? Thanks for the help!

How do you design a BJT switch to ensure it is (Vce) saturated.

Saturation current of bjt is a reference for us to adjust current of collector? If we want to operate in active mode, then we have to adjust the current of collector to under saturation level? Thank you

i have been asked in my lab report to calculate alpha in a bjt common emmitter circuit using 2 different formulas and explain why one is misleading.β=Ic/Ib= 537.1*10^-6/6.743*10^-6≈85 α= Ic/Ie=573.1*10^-6/566.357*^-6≈1.011 α=β/β +1≈0.988 i have worked out the two values of alpha where our beta...

Homework Statement See the jpeg image for the circuit. Question is simply determine the region of operation. The Attempt at a Solution The answer is cut off, but i don't really get how it is. Looking at the circuit, emitter voltage Ve should be higher than base voltage Vb...

Analyzing a BJT using pi-model

Fresh EE here that hasn't seemed to cover the main application of either a BJT or mosfet. When should you use one in place of the other? There doesn't seem to be a clear distinction between the two, however I would imagine there are substantional practical differences. Situation in...

I need help in answering the post lab questions given to us by our professor. 1. Is dc beta constant on every point of the characteristics? What is its effect in the linearity of the transistor? 2. What is the effect of a high dc beta on the characteristic curves? I have attached an...

Hi, I have a confusion with the saturation region of the transistor. Please help me out. It is commonly said that, the forward biased emitter-base junction and forward biased base- collector results in device saturation. Considering a PNP transistor as an example, forward biasing the...

Hello, I'm having some issues with small-signal analysis of BJT differential amplifiers. Let's say I have this BJT differential pair and suppose that Q1 and Q2 perfectly match: http://i50.tinypic.com/14ahdgn.jpg Suppose a small differential input is applied and consider the small–signal...

Hello, I'm studying BJTs and I have a doubt about deriving the output resistance in the small signal equivalent circuit. Let's consider the circuit below: To derive the output resistance, I'd write the following KCL: i_x = i_{rc} + i_c at this point, every example I've seen says R_o = R_c...

in common emitter configuration of BJT , why do we have linear relationship between output current (collector current ) & output voltage ( collector emitter voltage) ? Has it anything to do with early effect ? If yes then why don't we have linear relationship in case of common base configuration ?

help! Input output characteristics of BJT I have attached an image of the graph. Does this graph apply for both npn and pnp transistors. I have asked this because for pnp, the collector(c) and base(B) terminals must be reverse-biased at the active region, and B must be at a higher potential...

Lets take a simple BJR transistor having an Rc. The Ic = beta*Ib, of course. But Ic=(Vcc-Vce)/Rc as well right? Now the confusion, does Ib cause Ic or is Ib possible without Ic (and thus no Vcc)? If we have Vcc and thus Vce than we shall have Ic thus we can have Ib=Ic/beta? What causes Vce, is...

Homework Statement Consider the circuit shown below. A Q-point value for IC between a minimum of 4 mA and a maximum of 5 mA is required. Assume constant resistor values, and suppose that b ranges from 100 to 300. It is desired that RB have the largest possible value while meeting the other...

I get that collector current is fixed so as collector current goes up, the voltage drop across the collector resistor goes up and the collector-emitter voltage goes down. Which is why it is basically zero at saturation. But for ac it is not zero but negative when input is positive. why is this...

Why exactly is there zero current flowing through a diode when it is short circuited, given the presence of the barrier potential? My current understanding is that the drift current precisely balances the diffusion current. But if you take a diode and short it with a wire, wouldn't you then also...

Hi, This is my first post in the forum. :) Why is the saturation voltage of a transistor equal to 0.2 V? Why not a lesser value? During saturation the base is filled with majority carriers and the barrier potential is absent. Hence the voltage should be 0V, right?

Hi, Everyone. I have an electronics I exams tomorrow, and I'm looking for help in solving the following exercise if you don't mind. The exercise tells that this circuit is to be fabricated with a transistor type whose β is in the range of 50-150. It asks to find the value of Rc, so...

I have three doubts in BJT: 1). in BJT Ie=Ib+Ic ; Ie-emitter current; Ib-base current; Ic-collector current then i find in many circuits, collector current is given to load, if the emitter current is greater than the collector current, we can connect the emitter terminal to the load, to get...

I'm trying to understand transistors so I bought a couple and have been doing some reading, I basicly got it but some quick experiments have me dumbfounded.. I have the most basic NPN transistor circuit setup http://amasci.com/amateur/transis2.html like thatone, only with a loudspeaker...

Hi. I was just wondering about when I'm doing small singla analysis with Bipolar Junction Transistor (BJT) is there a basic rule on which model to use, the Hybrid Pi or the T-model?

Homework Statement Working with BJT analysis, and varying models for the analysis. Prove r_{0}=\frac{V_{a} + V_{CE}}{I_{C}}, where r_{0} is the resistance for the Early model. I haven't been able to find a circuit or much of anything about this, let alone proving it. Homework Equations...

Hey all, If I understand correctly, transition frequency is synonymous with the unity-gain bandwidth frequency. With that said, if you divide the gain at the operating frequency by the transition frequency, you should get the operating frequency. Please correct my logic if I am incorrect...

Say you are given the problem of constructing the charge density vs position graph of a BJT(lets take a NPN BJT under equilibrium conditions for example). Now, it is a given as to how a NPN BJT Energy Band Diagram would look like through intuition or a google search. Using only the information...

i got this example from our lecture notes, there is one thing i don't understand, When calculating Ve, he takes Vb and minus the Voltage drop across transistor, so 2V - 0.7V and gets 1.3 V for Ve, my confusion is why did he ignore Vc? should it not be (Vc + Vb)-0.7V ,so...

Hi! Can anyone recommend a text that goes through calculation in fall time, rise time, saturation time and final rise time thoroughly with some examples provided? I've looked through microelectronic circuit design by Jaeger / Neamen, they briefly mention the concept at best but do not have...

Hi all, I have a doubt regarding saturation mode of BJT. Saturation occurs when both emitter-base junction and base-collector junction gets forward biased. For forward biasing a silicon p-n junction only 0.7V is needed. So is for emitter-base junction. But not for base-collector junction...

Homework Statement a)Find R1 b)Find the change in IC if Re varies by 5%. Given: Ic = 0.25mA β=100 (see attached ckt) Homework Equations The Attempt at a Solution Ic=0.25mA, Ib=0.0025mA Vbe = 0.6956V Ie=Ic+Ib = 0.2525mA Re = 200*0.2525 = 50.5mV Found R1 by applying KCL at...

Homework Statement Find IB, IC, IE, VCE, VBC, and VEB for the NPN transistor in the circuit below for β = 50, 150, 500. Let VCC = 10 V, R1 = 100 KΩ, R2 = 400 KΩ, RC=2 KΩ, and RE = 0 Ω. Assume VBE = 0.7V.Homework Equations V = iR IE = Ib + IcThe Attempt at a Solution My question is that if RE...

Homework Statement Given, β=100, Is = 6E-16 See attachment. a) Find min value of Rb such that the BJT is in active region b) For the Rb found, what is the base-collector voltage if β=200 Homework Equations The Attempt at a Solution Assuming, VCE min for active region operation...

Hello Forum, question about BJT transistors: some books say that they are current (base current) operated... Some other books state that the emitter-collector current is controlled by the voltage between the base and the emitter...which one is correct? FET are voltage controlled... Holes...

[b]1. Homework Statement my teacher wants me to design a circuit to control the on or off of 4 BJTs in the circuit. Homework Equations The Attempt at a Solution so i tryed to control a BJT at once .. it workshttp://user.qzone.qq.com/259234914/infocenter#!app=4 but there were...

A bit confused about direction of current flow in the BJT equivalent ckt. I'm trying to calculate the resistance seen, looking into the emitter terminal. In what direction does the current flow in the bjt output resistance ro?

In the equivalent diagram of BJT, Vbe and rbe represent the base voltage and resistance. gmVbe is a current source, which represents the current gain. Since gm = Ic/Vt Vt/Ic = 1/gm Does this mean the impedance of the current source is 1/gm ? I know this sounds a bit weird. It's because...

Homework Statement Find input resistance of the ckt (see attached) Homework Equations The Attempt at a Solution Q2 is diode connected, so I replaced Q2 with VBE resistance (rbe or r∏). So, Rin is rbe1+(β+1)rbe2 But the answer is somewhat different, it's rbe1+ (β+1)...

A BJT with emitter degeneration resistor reduces gain. To overcome this we can use a bypass capacitor, so the small signal gain is not reduced. How do you pick this capacitor? Should it(the capacitive reactance) be less than RE or 1/gm. I don't understand why it should be less than 1/gm.

Attached is an image of a typical BJT current mirror. The reference current is established by the resistor. We can calculate R with: R = (V.CC - V.BE) / I.REF Now what I don't understand: I know I.C = I.S * e ^ (V.BE / V.T). The collector current is quite sensitive to changes in the...

For a BJT with voltage divider bias (but without emitter deneration resistor), what is the beta dependence? Ib is (Vth-Vbe)/Rth [where, Vth and Rth are thevenin equivalent of the divider) Ic = β * Ib The above is almost same as just base bias, where a resistor from base is collected...

Hello all, Just recently my one Professor has been depicting the BJT transistor with a capacitor joining the base and emitter portion of the transistor. The transistor is of npn configuration, however, he has yet to say anything regarding the capacitor. Is this "capacitor" a characteristic of...

Now as you can see in the picture a common base configuration of BJT. The green markings in the picture are resistances. :p My question is: By KVL : VBB = VBE + IE*RB which means that IE is esentially a constant because VBB , VBE, RB are constants. Now If Voltage Vcb is increased Early...

I'm trying to understand emitter degeneration. Instead of the entire input applied across just the VBE junction, it is now applied across the VBE junction plus an emitter resistor RE. So when collector current increases, some additional voltage is dropped across RE, so that voltage across VBE...

For the BJT in the reverse active region, why shouldn't you dope the emitter and collector almost equally, even though it will increase beta_r? Also, what are some ways you can increase beta_r (in reverse active) or beta_f (in forward active)?

I was looking at input stage of 741 internal ckt - http://en.wikipedia.org/wiki/File:OpAmpTransistorLevel_Colored_Labeled.svg how exactly are the 2 transistors Q1,Q2 biased? I looked at bjt differential input stage wiki here -...

May i know what is the use of the npn and pnp bjt for my schematic? can someone please advise. Thank You

Hi, I'm having some trouble determining whether or not a BJT (used in an amplifier topology for example) is in forward active, given that we don't know what the base-emitter and base-collector voltages are (we might know how they are related). My textbook likes to argue: assume it is in forward...

I've been looking some pre-biased dual NPNs to use as buffers. My criteria is to have a very small package (i would prefer their width be less than 3mm. 2mm is very good) and that they ought to have a max. collector current rating of 200mA. I may have found such an NPN in the...

All the models I see is mostly common emitter, I have a circuit with AC equivalent shown in Fig a. Where v_s \; is the signal voltage and the source resistance R_s. I want to calculate the equivalent input noise voltage. Here is what I attempt to do it: 147190[/ATTACH]"] I show the equivalent...