Questions tagged [biasing]
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1answer
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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 ...
2
votes
2answers
61 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 ...
0
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1answer
60 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 ...
3
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1answer
70 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
69 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
48 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
59 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 ...
0
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1answer
54 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 ...
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0answers
32 views
Compensating transistor biasing
How to analyze the quiescent conditions of the circuit below assuming the tansistors are on an array such as CA3096? (Fig 5N.21 from Learning the Art of Electronics)
Both emitters are at ground, so ...
2
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1answer
56 views
How to choose RF choke in the biasing circuit of varactor-tuned resonant circuit
I am new to circuit and has a very basic question about how to set biasing circuit of varactor. I need to use varactor to tune the resonance behavior of Split ring resonator (SRR) structure when ...
0
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1answer
158 views
Forward biasing of a BC547 transistor doesn't turn on LED
I have a setup as shown below:
simulate this circuit – Schematic created using CircuitLab
I am using the transistor as a sort of a switch. I am ensuring about 0.7 V (approx) is provided from ...
0
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1answer
117 views
Help with design a mic preamp with opamps for PGA and ADC
I want to sample an audio source using an electret microphone and analyze the spectrum of it with a uC. I'm interested in the 100Hz-2.5kHz range, so I calculate with these values when I tried to ...
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1answer
692 views
Biasing high frequency BJT cascode amplifier
So far, no one in the course has gotten both primary spec: 14.125 (with 1 V/V swing either way) nor 3dB-bandwidth of 500kHz to 20MHz using the 2N4427 (datasheet).
Vcc = 9V
I_CQ = 10mA-15mA
I have ...
0
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1answer
104 views
How to bias MOSFET for finding S-Parameter simulation?
I wanted to use a BSIM4 model of NMOS in my circuit. I got the correct dc biasing point, certain VDS,VGS and IC. But I am having issues measuring S-parameter data for MOSFET amplifiers. I simulated ...
3
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2answers
247 views
How do coupling capacitors in transistor not affect biasing?
I understand the usefulness of the capacitors in an amplifier circuit but i dont understand why we use one at the input? and how does this not affect the biasing if it removes the dc voltage?
Thanks.
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1answer
36 views
Confusion with understanding the fixed bias circuit
Below shows a bipolar transistor in fixed current bias configuration. A text says that this topology is independent of β:
What I understand is, since Vcc, Vbe and Rb is constant the base current ...
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0answers
65 views
Does applying dc bias to a signal make it stronger?
I worked on a device that mimics a triode vacuum tube. But it doesn't use any vacuum, instead, it uses an electrolyte. I got several of them working, and I can make them switch, by making the "grid" ...
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4answers
186 views
why is the feedback or gate resistance RG necessary?
Here the large feedback resistance RG interposed between gate and drain of the NMOS (usually in the megohm range) forces the dc voltage at the gate to be equal to that at the drain (because IG = 0). ...
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1answer
36 views
Verify bias voltage with no load
I have a device that can be configured to maintain a specific bias voltage on the output. How should I verify if it actually generates that specific voltage?
I do not think I could simply use a ...
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2answers
233 views
Biasing an IC CC-CE cascade amplifier
I have the following CC-CE (Common-Collector Common Emitter) cascade amplifier:
I am trying to bias the amplifier by using LTSpice. Here is my schematic below:
Apparently, from the displayed ...
0
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1answer
58 views
Bias Tee design for 150V AC and 150 DC at 40 - 50kHz
my question seems to concern a really easy device. But since I am new to this field of the magical electrons I am very eager to be careful and thankful for any help.
My task is to power an ultrasonic ...
0
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0answers
23 views
Current stability factor in terms of resistors in a biasing circuit
For the following biasing circuit:
A text gives the stability factor as:
Above S is defined as dIc/dIcbo. But how is the second equation above is derived from the first equation?(How is S is derived ...
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2answers
229 views
Emitter resistance in transistor bias
I am having issues with the emitter resistance during biasing of the transistor. Can someone explain me what's the point of using this resistor? It is getting very not intuitive for me.
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3answers
77 views
How can I “filter out” a small offset current from a current source?
I have a current source that produces a 1 kHz 1 mA sinusoidal current. Unfortunately it also outputs a small DC offset current (microamps). The current source does have a small trim pot to zero out ...
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3answers
4k views
What is a self biasing of a transistor. Explain with a circuit of it
There was a question in my semester exam. "Define stability factor. Explain self-bias circuit with diagram and derive expression for stability factor."
Now after searching a bit I found that when the ...
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0answers
368 views
Output Voltage Minimum Limit of LM358 as Error Amplifer
I am using one side of the LM358 as an error amplifier with a gain of 1, biased according to this MIT lesson for differential amplifiers.
The results below show me tuning the reference signal to see ...
1
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1answer
194 views
How to Bais a tuned rf amplifier and compute I/O Impedances
Can anyone point me in the right direction on how to implemented the depicted tuned r.f amplifier? Since the load resistance at the collector is replaced by the LC tank how does one go about in ...
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0answers
124 views
When to bias diodes in double balanced ring mixer?
Do I need to bias up the didoes in a double balanced ring mixer?
Some diodes have turn on voltage at 0.3V, and some turn on at 1.2V. If LO power is about 5dBm (~0.6V peak voltage), I would need extra ...
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3answers
215 views
How to bias a voltage for an ADC
I am part of a project that is implementing a power storage system. The storage device voltage must be monitored in order to direct power. The storage device voltage should remain between 12 and 36 V. ...
4
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2answers
4k views
BJT Voltage Divider Bias Circuit problem
Let's say we have the following circuit:
The known values are: \$\beta=100\$, \$Vcc=2.5V\$, \$V_A=\infty\$ (meaning the Early effect is not taken into account), \$V_{BE}=0.7V\$, \$I_S=8\cdot10^{-16}A\...
0
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1answer
251 views
DC analysis of common-drain NMOS amplifier
The DC analysis is regarding the amplifier calculations, but that is not relevant to the topic. The equivalent DC circuit of the amplifier is:
The known values are: \$Rg1=300k\Omega\$, \$Rg2=200k\...
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2answers
134 views
Pre-amplifier biased to one-half of power source
There is a schematic of an pre-amplifier that use one-half of voltage source output biasing (T1 emitter is one-half of V1). How the resistive network was calculated to allow one-half output Q-point?
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2answers
1k views
Difficulties in biasing MOSFET push-pull amplifier
Everything works perfectly well and following the expected in the simulations on MultiSim.
This is what the test-version of my circuit project looks like:
I made this version of the circuit to ...
2
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2answers
276 views
RF mixer theory and short circuits
Suppose I have the following RF mixer circuit-
How does placing two AC voltages of differing magnitude and frequency directly in contact with one another not create a short circuit condition in a ...
1
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2answers
472 views
Wide Swing Cascode Current Mirror Biasing Difficulties
I'm working on designing a cascode current mirror, depicted below:
Constraints: all Von needs to be above 200 mV, all Vds neds to be at least double Von, L is 0.35 um.
Derived from the SPICE file, k'...
0
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1answer
430 views
Biasing MOSFET with Constant Current Source
In the course of researching tube amplifier designs, it seems like a common technique to bias a MOSFET in an output stage using an LM317 configured as a constant current source, such as is given in ...
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6answers
2k views
Difficulties with Class B Amplifier Biasing
Here I am referring to class B output power amplifier.
This circuit should be easy to build and understand but I'm having problems with biasing since I don't really know how to bias the bases of Q1 ...
6
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2answers
1k views
Tube cathode biasing with CCS
I'm unable to understand how the biasing of the 12AX7 Tube in the schematic below works.
In particular, I can't understand how the LM334 can switch on, where does it find the required voltage to ...
0
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0answers
86 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, ...
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3answers
1k views
Differential Amplifier Biasing Problems
This is the circuit that I built: (desired voltage levels are described next to the circuit)
simulate this circuit – Schematic created using CircuitLab
I tried to make proper bias conditions ...
2
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2answers
691 views
How to conclude region of operation for a series combination of MOSFET
I understand that M1 is on and for M2 to be on the intermediate voltage(drain on M1 and source of M2) should be less than 1.5V. Also if M2 is ON then M2 is in saturation since Vds>(Vgs-Vt) for M2. Now ...
0
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2answers
508 views
How to make amplifier (almost) Beta independent?
There are several ways to bias the quiescent point of transistor, when used as an amplifier. Among which voltage divider is best known for its improvements (improved temperature drift and beta ...
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3answers
142 views
Low noise amplifier DC gain
This circuit provides 30dB gain to a 100kHz signal with a 10k input impedance. Is capacitor C2 necessary to suppress DC gain or is it redundant with the AC coupled input?
I would also like to make ...
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3answers
171 views
BJT AC analysis [closed]
Why while performing bjt's AC signal analysis we consider the base current as same as it is derived due to DC biasing of bjt(when there is no AC input applied),the applied AC signal must change its ...
9
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6answers
4k views
Why won't this PNP Transistor trigger?
The circuit below should be taking a 3.3V signal from an MCU on MCU_LS12 and outputting a 12V high-side signal.
The output is always 12V. On scoping the base to the output transistor is not being ...
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1answer
158 views
Improved Differential Amplifier
I made this circuit as shown below:
simulate this circuit – Schematic created using CircuitLab
After those improvements with current mirror and constant current source were considered, this is ...
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0answers
48 views
Differential transistor stage current not changing with temperature
I asked similar question recently, which also referred to differential transistor pair, but this one is different.
I made this circuit (in real world):
simulate this circuit – Schematic ...
18
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2answers
1k views
AB Without Diodes
Looking at another question about an AB Amplifier stage the answer was the classic diode biased push-pull stage like this... which I voted up like others..
simulate this circuit – Schematic ...
0
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1answer
555 views
Dual Feedback Transistor Biasing a Common Emitter Amplifier
I was reviewing/following a tutorial describing the pros/cons of various transistor base biasing configurations. Configuration #4 is shown above. Resistor Rb2 was added to what was previously ...
0
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1answer
88 views
Voltage biasing problem
How can I solve this question?
In the circuit below, the n-channel MOS device operates according to the equation:
i(D)=K(v(GS)−vT)^2,
where K is 9.2 milli-siemens per volt, vT is 0.5 volts. The values ...
