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0
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0answers
36 views

What would be the difference in the voltage transfer curves of this two circuits, assuming the op-amps are not ideal?

How does the resistor connecting the non-inverting terminal to ground affect the transfer curve?
1
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3answers
63 views

Behaviour of Voltage on Base in a fixed BIAS Common Emitter Amplifier

I'm having some trouble understanding the behaviour of the basic common emitter fixed bias amplifier. I've been looking at this for awhile now and I'm starting to think there is a foundational ...
0
votes
1answer
259 views

when a diode is forwards biased can current flow backwards through it?

when a diode is forwards biased can current flow backwards through it? this question comes from me trying to understand class AB amplifier biasing, so any additional comments about the diodes' use ...
0
votes
1answer
50 views

how to adjust drain bias to keep power dissipation constant (HEMT)

I am reading a chapter in a thesis about using HEMT (high electron mobility transistor) as a cryogenic amplifier. The measurement scheme is to use the gate voltage fluctuation's influence on the drain ...
1
vote
3answers
407 views

Gilbert cell biasing

I'm new here so I'm going to make is as simple as it can get.. How can I bias a Gilbert cell with bjt transistors like this one: What methods can I use to bias the transistors? Is there any example ...
0
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2answers
274 views

Why wouldn't my latching switch circuit turn off?

I built this latching switch circuit: https://www.edn.com/design/power-management/4427218/Latching-power-switch-uses-momentary-pushbutton When I connected it to my project (~140 LEDs) I found that I ...
0
votes
2answers
342 views

Understanding Minimum Output Voltage of Cascode Current Mirror

I guess that I have some serious trouble understanding how to get the saturation equation for the cascode current mirror right which is known from all the textbooks as $$ V_{out} = 2 V_{DS, sat} + V_{...
0
votes
1answer
32 views

How to connect two (or more) BJTs (collector of Q1 to base of Q2 for instance) and still make their bias voltages independent?

The question is in the title. I'm learning about how to use BJTs and was wondering how I could connect them in blocks the way bias voltages (thus operation modes) are not being dependant. Thank you!
0
votes
1answer
85 views

DC voltage in collector after active load

I am trying to analyse the DC Q bias point of the following circuits with a current source/mirror involved. I do not know how to calculate by hand the Q2 and Q5/Q4 collector voltages. All the currents ...
0
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0answers
96 views

Common emmiter amplifier collector current selection when using a current source to achieve symmetrical output swing

I know how to bias a common emmiter configuration when using resistors, my main interest is biasing the transistor in a way that maximum symmetrical output swing is achieved, when using resistors, ...
0
votes
1answer
116 views

What would happen to the DC bias voltage of the emitter if this capacitor is omitted?

I'm not quite sure what the question means. I need to explain what would happen if I removed the \$1.0 \mu F\$ blocking capacitor from this circuit. Howver, I'm not sure what the "DC bias voltage of ...
9
votes
2answers
3k views

Input coupling to Class AB amp with diode bias. One capacitor or two?

When AC coupling the input signal to a Class AB (Push-Pull / Complementary Pair) which is diode biased I see two different approaches: Signal connected between biasing diodes with single decoupling ...
2
votes
3answers
599 views

Biasing of a circuit with two transistors BJT

I need to calculate the bias values. So far I have only written these equations, but something is missing. (\$\beta=200\$ for both transistors and \$V_{BE\,on}=0,6\,V\$) Capacitors=open circuits \$\...
1
vote
2answers
2k views

Setting the bias for the power amp section of an audio amplifier?

I've been working on the internal amplifier of SW-12 active subwoofer. I started suspecting its power amp section may not be working properly. (I get musically coherent sound out of the attached ...
0
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2answers
1k views

Transistor bias circuit for 2N3904 - why some popular transistors does not work?

I have set up the simple common emitter amplifier circuit based on 2N3904. The circuit was first simulated in Multisim and than breadboarded. All works fine as expected. I have tested about 20 ...
0
votes
2answers
1k views

Emitter follower biasing with voltage divider

I have met a emitter follower design example in the Horowitz-Hill's book (scheme is below): And I don't understand why the resulting steps is correct: Step 1. Choose \$V_E\$. For the largest ...
0
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2answers
426 views

Voltage divider bias (Role of Coupling Capacitor)

simulate this circuit – Schematic created using CircuitLab Why does the voltage divider in second circuit (middle) has no impact? Vo is always equal to V4(correct me if am wrong). And once a ...
0
votes
3answers
581 views

Why are all the DC biasing sources assumed as ground in BJT transistor h-parameter equivalent model?

For example consider the first image on this schematic: Source: http://www.zen22142.zen.co.uk/Theory/tr_model.htm. Vcc is assumed as ground for ac equivalent circuit and thus RB1 and RB2 becomes ...
1
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3answers
498 views

Voltage divider types question

I have been studying different schematics ive found online to try to get a better understandment on the subject. Recently I came a voltage divider across that consisted of a transistor and a resistor, ...
0
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0answers
255 views

Choosing proper CCS current for discrete transistor amplifier's differential and VAS stages

Here is a figure from "Audio Power Amplifier Design" by Douglas Self. Self using almost same current values (4mA and 6-8mA) in many examples without explanation. How to choose these values properly ...
-1
votes
2answers
188 views

Calculating resistor values for an amplifier

How do we calculate the value of the resistors Rb and Re? The information given are limited: (β = 600) Ic = 10mA. It is always preferred to have a symmetrical output voltage swing.
1
vote
3answers
1k views

How can I identify transistors with a low Vce-sat (collector-emitter saturation voltage)?

I want minimum voltage drop between collector and emitter as I have very small Vcc voltage to supply the load. My Vcc is 3.3 volts. I want to use this switch to turn on/off 3 LEDs connected in ...
0
votes
1answer
187 views

Biasing a transistor

When biasing an AC Transistor amplifier circuit, does it bias the AC current/voltage by shifting the output wave up, or does it actually amplify it and change the amplitude of the output wave?
0
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1answer
674 views

How does an RF transistor bias work?

In many RF applications I have seen transistor circuit that looks something like this: simulate this circuit – Schematic created using CircuitLab Now, I understand the role of all the ...
0
votes
1answer
391 views

Common Emitter amplifier Bias Circuit Simplification

This is a slide from one of my semiconductor devices lectures. I understand how the bias circuit works and how to calculate the resistor values however I do not understand how this simplification ...
0
votes
1answer
148 views

BJT Transistor Biasing

For normal operation it is said to remember: Emmitter Base junction is always forward biased Collector Base junction is always reverse biased Can someone explain to me what this means? My view is ...
0
votes
2answers
660 views

Why is the collector- emitter voltage (Vce) not getting biased?

This question is an extension for my previously asked question here: Why is the voltage across collector and emitter pushing itself to 0.7 volts? A colleague of mine suggested that I take a look at ...
4
votes
3answers
1k views

What is the precise definition of forward and reverse bias for a P-N junction?

I have always thought that for a P-N junction, forward-biased simply means that \$ V_{PN} > 0 \$ and reverse biased means that \$ V_{PN} < 0 \$. However, in this article about NPN BJTs, there ...
1
vote
2answers
171 views

Calculating base current

The task is to find the operating point of this transistor: Given information: \$E_{C}=12V\$, \$V_{BE}=0.6V\$, \$V_{IN}=5V\$, \$\beta=200\$, \$R_{B}=440k\Omega\$, \$R_{C}=5k\Omega\$, \$R_{E}=3....
1
vote
4answers
732 views

Voltage Divider Bias

I am new to biasing calculations and I cannot understand why in a voltage divider bias we can apply the Thevenin Theorem to find the potential in the transistor base. For example, here http://www....
1
vote
2answers
1k views

Why Beta value is changing and very low in this circuit

I am simulating a circuit in Proteus 8.1 and I am getting very low value of Beta (16 in this case). It is changing depending on the resistances. Can you please guide what is happening here? d
1
vote
1answer
4k views

The advantage of using base biasing over emitter biasing?

Can someone please explain to me what is the advantage of using base biasing over emitter biasing. Why is a 'feedback resistor' used in base biasing?
2
votes
1answer
2k views

Any tips on designing an audio preamplifier for low frequencies?

I'm currently trying to design an audio preamp with the purpose of amplifying very faint audio signals (possibly in the microvolt range) from 20-200Hz. I've tried both transistors and op amps for ...
1
vote
3answers
205 views

Common emitter amplifier biasing and resistor selection

I'm designing a standard common emitter amplifier. My textbook states that it's standard to make \$V_C = 2/3 V_{CC}\$ and \$V_E = 1/3V_{cc}\$. I understand that it has to with maximizing the voltage ...
0
votes
1answer
226 views

What's the usage of this type of biasing?

I'm trying to know What's the usage of this type of biasing BJTs. this is the main schematic. I'm talking about these type of biasing: Another question to me is this type of biasing for potentiometer:...
6
votes
5answers
4k views

Is there any advantage to biasing a transistor with a zener diode rather than a (resistor-based) voltage divider?

In the figures below, we see two methods of biasing a bipolar transistor: the first uses a voltage divider, and the second employs a zener diode regulator. Since the voltage regulator appears far ...
1
vote
1answer
8k views

How to find the Q point of the NMOS transistor in Voltage-Divider Biasing Circuit?

The following is the circuit needed to be analyzed to find the Q point(\$V_{GS_Q}, V_{DS_Q}, I_{D_Q}\$). \$V_{TN}=1\text{V}\$ \$K_n=0.5\text{mAV}^{-2}\$ simulate this circuit – Schematic ...
6
votes
3answers
500 views

A question about Transistor in forward-active biasing?

I have question about transistor biasing. Between picture 1 and 2, what's difference, why we add the resistor RE in pic 2 ? what's it effect to circuit ? Similarity for pics 3 and 4, instead of ...
-1
votes
1answer
3k views

JFET voltage divider bias calculations

Hi im having some trouble with knowing how to perform calculations for \$I_D\$ in a simple JFET where it is biased by means of a voltage divider. I understand that use of the equation: $$I_D = I_{...
0
votes
3answers
141 views

what exactly is biasing in transistors and how to do biasing

I have read that collector, emitter must be reverse biased in CE configuration in npn transistor but how can n and n be reverse biased
0
votes
1answer
350 views

Why is the signal inverted on a VDB transistor?

I've got a 3904 connected in a voltage divider bias. Probing the input and output I notice that the output signal is inverted. Would someone explain the interworkings of how and why the output ...
1
vote
1answer
172 views

Would you help me understand this simple circuit?

I have three questions: Is it common emitter or common collector (emitter follower) or something else? How do you recognize it? What is the function/usage of R1 and C1? Are they for biasing the ...
2
votes
2answers
1k views

What does it mean for a transistor to be biased beyond cutoff?

I understand what it means for the transistor to be biased for Class A, AB, and B with regards to the location of their DC operating points (\$I_{C_Q}\$ and \$V_{CE_Q}\$ are found by finding the point ...
0
votes
1answer
2k views

Cascade BJT [ Exercise solve ]

How can I solve this circuit for \$\beta = 100 \$ , \$V_D = 0.7V \$ and \$V_{BE}= 0.7V\$ and arrows go to power \$V_{DD}=9V\$ simulate this circuit – Schematic created using CircuitLab general ...
0
votes
2answers
3k views

Explanation of transistor amplifying action

I am reading "Electronic Devices and Circuit Theory" by Louis Nashelsky, Robert L. Boylestad. I am not able to grasp article 3.5: Transistor Amplifying Action. I've mention some particular points on ...
2
votes
2answers
3k views

Control relay from sensor output when LOW is 0.2V

I used this circuit as a reference to drive a relay from the digital output of an arduino. This circuit worked as expected. simulate this circuit – Schematic created using CircuitLab ...
-4
votes
1answer
285 views

Transistor biasing [closed]

I have learnt loads about biasing a transistor, but I never managed to understand them. They talk about DC load line, Class A, B, C and various types of biasing. What are they all about and where can ...
3
votes
1answer
1k views

Why amplifiers (RC coupled) are based on voltage divider bias?

What actually determines the type of bias to be used for different practical applications. Also I do not get the point of using capacitors (coupling) for emitter current and high input resistance. If ...
6
votes
1answer
2k views

Transistor with emitter resistor calculation

I can't seem to get over this but this seems to be the basics in electronics. I have an NPN darlington transistor TIP122 and have built to simple test circuit around it with Rb = 150 ohm, Rc = 80 ohm ...