Questions tagged [biasing]
-1
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0answers
58 views
Determine the voltage transfer characteristics of the bjt
How do I start this question, I've just been trying to plot vin vs vout and using EBJ<0.5 and CBJ>0.7 and trying to get a range for vin and plotting? Is this the correct way to go about this?
0
votes
1answer
59 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
votes
1answer
74 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 ...
3
votes
1answer
356 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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0answers
43 views
Variable Negative Bias for MOSFET Gate Drive
I am looking to generate a negative gate bias voltage for a GaN HPA I will be using for one of my projects. Per the datasheet, the typical off state (pinch-off) gate voltage is -7V, and the operating ...
0
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1answer
30 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
152 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.
0
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1answer
33 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 ...
0
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0answers
63 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" ...
0
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4answers
104 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). ...
0
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1answer
35 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 ...
-1
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2answers
146 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
votes
1answer
51 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
22 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 ...
0
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2answers
93 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.
2
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3answers
71 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 ...
-3
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3answers
3k 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 ...
0
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0answers
139 views
Isolating DC ground and RF ground
A DC biasing circuit (cct) of a PIN-diode terminating a parasitic microstrip patch antenna needs to be designed. By parasitic I mean that EM field would be induced on it by a nearby lying another ...
1
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0answers
262 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 ...
0
votes
1answer
125 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 ...
0
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0answers
81 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 ...
0
votes
3answers
155 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
3k 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
votes
1answer
182 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\...
1
vote
2answers
119 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?
...
1
vote
2answers
823 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
votes
2answers
219 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
vote
2answers
372 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
votes
1answer
363 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 ...
7
votes
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
votes
2answers
898 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
67 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, ...
4
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3answers
873 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
votes
2answers
442 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
votes
2answers
387 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 ...
1
vote
3answers
117 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 ...
-1
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3answers
152 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
votes
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 ...
-1
votes
1answer
140 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 ...
0
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0answers
44 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
votes
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
votes
1answer
462 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
votes
1answer
86 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 ...
0
votes
3answers
188 views
Determining base-emitter voltage in a CE BJT with base supplied by constant current source
I apologize in advance for posting a homework problem. I am given this simple BJT circuit as shown below. I have to find the base-emitter voltage with reverse beta equal to 0.5 and forward beta 50. ...
0
votes
0answers
120 views
Resistor vs diode in power supply bias
In my circuit I have a input voltage between -100 to 100 mv (roughly). I want to make the voltage go through a voltage buffer (an emitter follower) connected to a 9V battery (so Vcc=9V). I would then ...
0
votes
1answer
259 views
Op-amp variable reference voltage
Is it appropriate to trim signal offset to an op-amp using only a divider and a trim-pot? For stable operation would it be preferable to connect drive the potentiometer from precision references or ...
1
vote
4answers
1k views
MOSFET Basic Biasing Problems
After a lot of theoretical studying of MOSFETs, I decided to try out at least the basics of it in practice.
Here is the first circuit I ever made using MOSFET:
simulate this circuit – ...
0
votes
2answers
247 views
Need help DC biasing an AC source
I am trying to simulate this circuit I saw here:
However, when I simulate it, the "mid-point" does not behave like the blue line in the above picture. You can check the simulation here:
Is the ...
1
vote
2answers
208 views
Simple MOS current mirror bias circuit
Consider the basic MOS current mirror bias circuitry
I am really trying to understand on how Vbias when M3 is 'on' can be any other value other than Vt because M3 is diode connected (Vds= Vgs) and ...
0
votes
1answer
480 views
Adding a DC bias to an AC signal for amplification and measurement
I am trying to add a DC bias to this AC signal, but for some reason the schematics I found online for this do not work. The AC coupling is not happening.
I have simulated the circuit here: http://...
