# bjt

1. ### Engineering Computing resistance in given circuit with BJT

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...
2. ### Engineering Determine the input impedances of a circuit

1. 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: 2. Homework Equations 3. The Attempt at a Solution To determine the input resistances I...
3. ### Difference between h-parameters and hybrid pi?

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.
4. ### I Straight line plot of bipolar transistor - temperature?

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}...
5. M

### Capacitors in Hybrid-pi Model and Frequency Response

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...
6. ### Ohmic Resistance

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...
7. ### PNP Transistor voltage calculation

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...
8. ### BJT and MOSFET complete analysis

1. 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...
9. ### Engineering Analog electronics (BJT circuit analysis)

1. Homework Statement For beta = 100 and assuming ro is very large, what is the DC voltage at the collector? 2. Homework Equations IB = IE(β+1) IC = β*IB 3. 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...
10. ### NPN BJT transistor: base voltage / emitter current

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...
11. ### Audio Amplifier Using TIP 147, 142

<< 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...
12. ### Need help in making my Electronics Project using BJT...

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...
13. ### KVL loop in BJT biasing

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
14. ### The collector current

1. 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...
15. ### BJT hybrid pi model,why "always" ro resistor is shown?

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...
16. ### Why would cascode amp oscillate?

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...
17. ### Engineering BJT analog circuit design

1. 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...
18. ### Temperature sensor with BJT?

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...
19. ### BJT Collector to Emitter voltage

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...
20. ### Engineering Designing a bias circuit

1. 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...
21. ### Basic Electronics: Transistor confusion

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...
22. ### BJT collector

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, thats alright , but, i dont get why Ic considered as the output? in NPN BJT...
23. ### How BJT transistor works (with conventional current notation perspective)

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...
24. ### BJT difference between equivalent circuits for large, small and pi hybrid signals

Hi everyone. im starting to study transisors at Uni. and im 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...
25. ### Determining h parmaters of bjt practically

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...
26. ### Bootstrapping Amplifiers, and Signal Bypasses

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...