Questions tagged [biasing]

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Biasing circuit - Voltage follower circuit

I am using MABC-001000-DP000L, which is and Bias controller/sequencer. I am using this for Providing gate voltage and drain voltage to the power amplifier. In the datasheet, it is mentioned that the ...
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0answers
46 views

Bias stabilization circuit

This is little bit harder to me understand, can someone simply explain me what is loading effect and how to solve this one
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2answers
87 views

Why can we bias MOSFET with current source?

My question is: If I have properly set VGS to prevent MOS from turning off, then if we biase a MOSFET with a constant current source, how can we conclude that it is working at saturation region? How ...
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0answers
51 views

Biasing circuit schematic - MABC-001000-DP000L

I am trying to design a bias controller circuit using MABC-001000-DP000L. I am unable to find the full schematic of the same. Has any one used MABC-001000-DP000L for designing bias circuit? Edit:- I ...
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1answer
59 views

Biasing of CE amplifier with emitter resistor for specific gain

I am trying to design a Common-Emitter amplifier to the following specifications: Midband voltage gain of 50 Frequency range 100Hz to 20kHz Load \$5k\Omega\$ with a coupling capacitor (not shown ...
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1answer
25 views

finding transconductance for common source amplifier

I wanted to check the transconductance formula I am using is correct when I am dealing with an amplifier that has a small signal (Vsig) and a DC signal(Vs). The schematic below is a little unclear but ...
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1answer
15 views

Can I use a buffer on my bias voltage net?

I'm a french stompbox / bass guitar pedal hobbyist, probably very bad at designing them. I've been thinking about bias voltage nets for some time, and how inefficient they sometimes are. I've studied ...
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3answers
67 views

Class C Amplifier: Calculating the base resistor

I've built a Class C amplifier for educational purposes and believe I understand the major concepts on how it works. The only piece I'm struggling with is how to calculate for the base resistor. From ...
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1answer
52 views

Troubles with mic preamp for headphones with integrated microphone

I am designing a preamp intended to interface with a microphone in common headphones (e.g. apple earpods, or sony headphones with a microphone) which will then connect to my ADC's inputs. I've ...
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1answer
47 views

Confusion on operation of bipolar differential amp (long tailed pair)

Let's say there's a basic differential amp constructed with two npn BJTs. And a current source is working as the tail. The task I have is to amplify a small AC signal of around 1mV p-p, referenced to ...
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1answer
56 views

bias a signal with DC input coupling, but without attenuation?

I want to bias the analog signal present on an MCU output pin. This signal varies between 0v and ≃3V, I need to shift it down to -/+1.5V range. Most importantly, I need to keep any DC offset ...
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0answers
32 views

Common emitter biasing

A quick question on biasing a common emitter. I am given the following circuit and asked to derive several things. I am provided with the information that the transistor is in the active region, so it ...
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2answers
55 views

AC coupling of a transistor

So we assume to have proper bias currents flowing in both of the two transistors. What is claimed by books is that a capacitive coupling will not change the bias parameters. But, we know that a ...
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1answer
55 views

How and in what chronological order did different transistor biasing circuits arise?

On the wikipedia page for BJT biasing, there are about 4 different biasing methods discussed. I can analyze and understand each one of them, however I want to know how and in what order people came up ...
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2answers
83 views

Bias stabilization of a transistor

The instability of Collector current(Ic) of a transistor depends on three factors viz. Icbo, Vbe & Beta. Can you explain why Vbe decreases(by 2.5 mV/°C) with increase in temperature?
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0answers
35 views

BJT conceptual doubt

I was given this problem in a problem set. I want to ask what will the voltage at Base when \$ \beta \rightarrow \infty\$. My answer to the problem - When \$ \beta \rightarrow \infty\$ then width of ...
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5answers
168 views

About transistor biasing and coupling capacitors in ICs

I'm trying to understand how biasing works in ICs. When using discrete transistors we are told to bias them using polarization circuits typically made of voltage dividers. Then ac signal is introduced ...
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3answers
101 views

In a class C amplifier, how does RB biases the base of transistor?

In a class C amplifier, I read that: "Resistor Rb is connected to the transistor Q1 base. A biasing resistor which connects to the base of Q1 try to pulls the base of transistor further downwards and ...
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2answers
85 views

Working of a transistor in a TTL inverter circuit

I was referring to TTL inverter circuit in the book Digital fundamentals by Thomas Floyd and its working principles first proposition went as follows: When input is HIGH, Base emitter of Q1 is ...
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1answer
73 views

Biasing a emitter follower darlington configuration

Below picture is a simple voltage regulator(link to simulator): The current at the op amps output is at nA region(why?), how can I increase the current at the op amps output without adding a third ...
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0answers
33 views

Initially on Power Control with BJTs

I've removed a voltage regulator from my circuit and replaced it with a series of BJTs. The regulator was just switching voltage. But I need the circuit (which happens to power/wake the micro) to be ...
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1answer
52 views

How to use a SPDT with no negative capability for audio signal routing?

I have a couple of SGM3005 chips and want to use them as switches in an audio circuit, but they don't support negative signals. The classical solution would be to bias the COM1 input, right? But, what ...
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3answers
82 views

Need Help debugging Colpitts oscillator

I've built the circuit shown in the picture on the breadboard. The simulation works as expected but when I build it i don't get any oscillations. I've measured all the DC voltages and they are as ...
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0answers
42 views

How does Q point affect gain

Let’s say I have a transistor class A amplifier circuit using a depletion mode FET. I have the load and the source resistor values already picked out to provide the right amount of gain and the source ...
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2answers
60 views

Differential amplifier with a current source

How to change the current source in the emitter here, so that the whole thing can be biased from a positive power supply (without the need for negative rail Vee) keeping all the other parameters more ...
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1answer
64 views

How to calculate cutoff frequency for a high pass filter in DC biasing circuit

I would like to DC bias an AC signal using a voltage divider as shown in the following schematic. I realise the bias point would be subject to noise from the power rails, but that is not a concern for ...
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7answers
990 views

Emitter resistor and biasing voltage

In many articles regarding transistor biasing I see a circuit like below and I don't really get what is the point of biasing like this WITHOUT emitter resistor Re? When emitter branch is connected ...
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2answers
216 views

Howland current source with voltage reference [closed]

I need a precision current pump for small ac signals(50uA) and i tried it in multisim with a howland topology. It works however i need the load to not be grounded but bound to a bias voltage. Here i ...
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1answer
63 views

Why is the effective base resistance important for the voltage divider BJT amplifier?

I came across many questions regarding the below type of biasing where they explain and analyze Rth Vth and conclude that Rth must be very small comparing to Rin. Rin is the effective resistance seen ...
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4answers
155 views

What exactly is meant by beta dependence in this fixed bias BJT scheme? [duplicate]

What I understand that, in a fixed bias BJT scheme the problem is beta dependence. Below is an example from a text: Now I read that this is not a good design. But I will still solve this by assuming ...
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1answer
63 views

Bias voltage of transistor [closed]

I would like to understand the purpose of biasing the transistor and why It has to be halfway between Vcc and ground? And which terminal of the transistor (Base, collector or emitter) should be ...
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0answers
34 views

Is Q-Point in Transistor constant? For different configuration if same transistor is used?

Via IV-Characteristics, for specific Ib, I got the Q-Point and using the same value of the Q-Point, I constructed a common emitter configuration biasing circuit that its V_ce = Q-Point_Voltageafter ...
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1answer
59 views

Deriving that Vin is way larger than nVt from Shockley equation

I am trying to show that from the Shockley equation Vin >> nVt. Given a simple diode circuit like this So far, I have equated the current through the resistor \$I = \frac {V_{in} - V_{D1}} {R_1}...
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0answers
40 views

Biasing an Enhancement NMOS with Gate-Source Connected

I'm working on a university project wherein a full-wave rectifier is constructed using two enhancement mode NMOS transistors. I'm tasked with designing a biasing circuit for the NMOS', but I don't ...
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1answer
42 views

Confusion regarding Fixed-Biased configuration of JFET

This is the picture of a fixed-biased JFET, taken from a book :- This is written in the book, relating to the above pic :- I am unable to understand why \$ V_{GS} \$ has a different polarity than \$ ...
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1answer
172 views

Voltage Divider Configuration of Transistor

I have a voltage divider configuration for biasing my transistor. The gain of transistor is lets say 150 which is typical value for BC547. What I want is limit the current flowing through the base to ...
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2answers
88 views

Why is Rc parallel to RL?

While determing the AC load line, the author takes Rc to be parallel to Rl. How is it possible since the two resistors have different nodes?
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0answers
52 views

Voltage Gain for Driver in Class AB Amplifier

Can anyone tell me how to calculate the Voltage gain for Q3 in the following schematic ? Is it the same method (or partially modified) like the one used for Class A amplifiers for Voltage gain ...
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1answer
119 views

Biasing in this FM transmitter

Here is a simple FM transmitter that I've been studying recently. What I'm wondering about currently is how the BJT amplifier in this circuit is biased. I believe that from the audio signal standpoint ...
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1answer
48 views

Amplifier Voltage

I'm studying for my electronics exam and for this particular problem I have: Av = –85 (V/V), Ap 21 (dB) power gain, Ap = 3.41 (W/W), L+ = +9 (V), L- = -6 (V). Now the next exercise asks that: ...
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1answer
55 views

Transistor Biasing of high side switching network for PWM control

simulate this circuit – Schematic created using CircuitLab iagramI am attempting to create a high side switching circuit for a string of LEDs wired in parallel. There are multiple strings, all ...
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2answers
568 views

Biasing a second stage amplifier

I built a two-stage amplifier as shown below. I have already built the first satge (R1-R5 & C1-C2) such that If I apply a signal of 1volts peak-peak, the output (at collector of Q1) would be 8 ...
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1answer
197 views

What's the purpose of the inductor in this microphone biasing schematic?

I'm just wondering what's the purpose of the inductor in this microphone biasing schematic? Could it be that I have very low input signal from the microphone because of missing L1? Bias generator ...
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2answers
96 views

Voltage reference vs voltage regulator

I need to bias some op amp inputs with a voltage. I’m in the 10-60 hz range. I need the bias voltage to be as low noise as possible, like -155 dbv . Would a voltage reference, voltage regulator, or ...
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1answer
68 views

Large ac input class AB biasing

I'm trying to bias the following circuit to power an 8 ohm speaker with an 8Vptp output. The following are the calculations I've done to get this current setup but the output is only good up to 1Vptp ...
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1answer
113 views

Constant-gm bias circuit

I am doing a study on Improvements in biasing and compensation of CMOS opamp. Do you guys know how to come up with the equation for RDS4C ?
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2answers
291 views

Why do we use one bias (VCC) for transistor amplifier circuits and 2 supplies for opamp circuits? [closed]

Opamps are said to have 2 supplies, so that the output can rail between these two points, then why do transistors have only one bias point.
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3answers
77 views

555 timer and biasing

Why is it that op-amps used as ICs, such as LM741 require a +Vcc and -Vcc for biasing whereas there is no -Vcc for a 555 timer? What determines the biasing for any IC?
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1answer
76 views

NPN transistor won't saturate when Vcc is greater than 7 volts

Am I missing something here? I have an NPN transistor (2N2222) with a 10K resistor from collector to Vcc. Also a 10K resistor from base to input signal. Emitter is grounded. The base input is ...
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1answer
63 views

How can a guy calculate the second collector current from this circuit?

This is an audio amp that we built for a project. I can easily find the first collector current from the first transistor by multiplying it with its Beta(200) and since the first transistor is beta ...