Questions tagged [biasing]
194
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How to bias the Q55, Q54 transistors in my design (what's the right voltage value needed for it)?
I want to make a simple differential amplifier and when I bias the pnp transistor that's connected to Vcc I notice in simulation that the application is too small (less than 1) and it go around 4.96v ...
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2
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Darlington transistor configuration
Can two 2n2222a transistors output more than 1amp of current if biased properly; supposing 1.4v to 1.5v is applied to the base?
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2
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Electrical characteristics on datasheet
What does this part of a datasheet mean? I always get confused when studying them...
Is the user suppose to meet these conditions before getting the results stated on the sheet?
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Transistor pin configuration
Is the base of a transistor (NPN) always positive or does it change due to manufacturers specs; as some might decide to put the base as pin 1 , followed by the rest; maybe collector as pin 2 etc like ...
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Do we require matching circuit and stability in Gilbert cell active mixer design? If yes then what is the procedure?
I'm trying to simulate a Gilbert cell active mixer using a PHEMT transistor model in ADS. I've referred some articles of Gilbert cell active mixer design but I haven't found any matching circuit or ...
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LTspice simulation doesn't match oscilloscope measurement; is the circuit diagram correct?
This box should add DC offset to a resonant circuit. I drew the simulation on LTspice. However, it's not similar to the result in oscilloscope. So, my question is: Is my circuit diagram correct?
#1 ...
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My RF amplifier circuit works in LTSpice. Will it work in reality, too?
I am working now for a while with bias calculations. I have found a good turorial to calculate it by my own and I have seen that there are already calculators on internet, which made my life much ...
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Impedance reflection in making a simple current source
I am making a constant current source using the transistor. I am a bit confused regarding the biasing of the transistor. I have seen in many places that when we are setting the biasing of the ...
user340506
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Variation in a BJT's forward current gain compared to variation in saturation current
(Questions summarized at the bottom of the post.) For discrete BJT circuits, a biasing scheme like the one below is often described which helps reduce the sensitivity of \$I_C\$ to variations in the ...
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Wide Swing PMOS Cascode Biasing
I would like to know if someone has designed a wide swing PMOS cascode biasing circuit (as attached in the picture) in 16nm FinFET, especially for IO devices having 1.8V supply. I see that ...
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What is the basic idea behind the so-called "diamond buffer"?
The idea for this question came about after I wrote an answer to a similar question. This "diamond solution" was something unknown to me. I took a look at Wikipedia page (see the picture ...
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Class AB crossover distortion diode fix
In the class AB amplifier shown below, we use diodes to make the PNP and NPN conduct equally.
How do the diodes make them conduct equally?
Is there some intuition I could use to understand this ...
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Why isn't my current mirror reflecting 500uA on each side?
I'm designing a telescopic cascode with a tail current source of 1mA. I had set my VDD to be 2V and all of the mosfets in the schematic seem to be saturated but the current reflected by the current ...
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Bias current of a MOS differential amplifier using two transistors
I am trying to understand the role of M14 and M13 transistors in the paper "Compact silicon neuron circuit with spiking and bursting behavior" by Jayawan H.B. Wijekoon, Piotr Dudek
(2008)
...
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Why is there current flowing into my JFET? [closed]
When I connect my JFET to a 9 volt battery and then short circuit the gate to the source via an ammmeter, it reads 6 mA of current. When I try biasing the JFET (BFW 11) with a 1 MΩ resistor the ...
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Biasing resistors for differential amplifier
I've an exercise where I've to design an unbalanced differential amplifier, and I'm given the circuit below and told that it's the basic one. I'm then asked to have the appropriate bias resistors.
...
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Base current in a fixed bias BJT
Why does the base current remain nearly constant, neglecting V(be) in a fixed circuit bias for a bipolar junction transistor with respect to temperature? If Rb changes with temperature, the base ...
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Issue with the gate voltage
Trying to generate Gate voltage and drain voltage from a card designed by me. Everything is generating properly except the gate voltage.
I am using MABC-001000-DP000L for VG AND VD generation
As per ...
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Can I read the voltage (MCU ADC) with an isolated power source by opamp inputs?
I made a conceptual design to read an industrial 2- or 3-wire temperature sensor with a single 3-connection terminal.
I used an opamp in differential mode to read two terminal connections which are ...
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How can I calculate R1, R2, RC and RE in the following silicon transistor circuit?
We have 4 unknowns, so we need 4 equations.
If we make the equivalent Thévenin circuit for R1 and R2, and by applying KVL on the input and outputs we get only 2 equations.
Rth=(R1×R2)/(R1+R1)
Vth=(...
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RS-485 bias & termination resistors with 3.3v transceiver and 100 ohm cable
I am trying to connect two boards together with a few feet of Cat 5e cable. Both boards will be using 3.3v RS-485 transceivers (ISL83483 or similar).
Using this calculator, I entered 3.3v for supply ...
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196
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AC voltage on DC voltage
In the voltage divider below, the voltage at point A is obviously 5 V. If we connect a 9 V DC voltage source between ground and point A, the voltage at point A will be 9 V. I think the same is true if ...
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Which model does this equation come from in fixed bias circuit?
In fixed bias circuit
I calculated voltage gain by this :
I measured the DC response in simulation as:
Ic = 3.73 mA
Ib = 15.7 uA
Vc = 11.3 mV
Vbe = 824 mV
I calculated re (ac emitter resistance)...
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Can collector feedback bias circuit explain with this block diagram?
Can the circuit above be explained with the block diagram below?
I found an explanation of this circuit in sequential so I think they come from block diagram so I tried to create block diagram that ...
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Output voltage for clipper circuit with bias
I've been working with diodes recently and I'm struggling understanding how to actually handle them in circuit. In general, I know that they only can pass the current in one direction because of how ...
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Does collector feedback bias work like this in real life?
I am reading about collector feedback biasing in BJT transistors.
Here is how it works:
Now suppose for some reason, a temperature change perhaps, β increases. This should cause an increase in IC. ...
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Finding the Q-point of a transistor: disambiguation
I find the definitions of Q-point that I have been given in class to be a bit ambiguous, so please read on and confirm or correct my understanding.
As I understand from this SO answer, the Q-point or ...
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514
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How is DC bias offset removed in a differential amplifier circuit?
Looking at the long-tailed pair, if we remove the dual supply and bias the amplifier for single supply operation it will generate a DC-shifted signal. How is this DC-offset typically cancelled for ...
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Biasing Circuit for MOSFET [closed]
I am struggling with a biasing circuit for my MOSFET. Can you help me?
It is hard to decide what kind of biasing circuit should be used. So my mind went blank. I hope the information in the picture is ...
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646
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LM324N comparator, why does the output not reach v+?
I am trying to use a LM324N as a comparator. Here is the circuit and the waveforms. As you can see the output does not exceed ~3.8V, why does it not go to 5V? Am I incorrect in expecting the output to ...
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Relation between collector current and Vce voltage in saturation mode
I have confusion regarding how collector current affects the voltage across collector to emitter in NPN transistor (2N4123).
How do I interpret this graph? Can I say when collector current increases ...
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HV Rectifier output for APD biasing
I am trying to convert low 5V or 12V to -200V using this device. Which converts it using transformer and rectifier at the output:
Can I just attach HV OUT to bias APD detectors? Or is there any ...
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109
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Can I bias a depletion mode FET with a diode?
I'm trying to work out how to bias a dual gate MOSFET that I'm working with. Its behavior is halfway between depletion and enhancement modes. That is, its ideal VG range is about -1.5V up to about 0....
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669
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How does class AB amplifier biasing work exactly? [duplicate]
Can somebody please explain in both cases the biasing method?
I don't understand the following points:
It's OK that we need ~0.7V for PNP and NPN base-emitter voltage, that's why a diode is used for ...
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What's the emitter voltage of a 2N2222 transistor with grounded base and a sine wave at the collector?
Consider this circuit with a sinusoidal source connected to the collector and a pulse toggling between 0 and 5 connected to the base of a 2N2222 transistor.
What I imagined the output being was when ...
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Class AB BJT biasing, diodes
Every time I see such circuits, it is assumed that the voltage drop across the diodes is exactly equal to Vj * 2. But this is simply not true. The voltage between the bases of transistors is highly ...
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349
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Simple push-pull BJT biasing
Explain me please, how biasing exactly works here?
From my view, on positive half of signal, we need about 0,7V + signal voltage (let's say signal is 1V) on NPN base, relative to its emitter=relative ...
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153
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What is the function of emitter biasing of a transistor?
I have been reading about transistor biasing to counteract inaccuracies in transistor manufacture, add stability etc.
One circuit I can't see the benefit in, which is diagrammed in the datasheet for ...
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Why is the depletion layer near the emitter region narrower than the collector region?
While studying Grob's Basic Electronics chapter 28 I came across this statement,
Notice in Fig. 28–2 that the EB depletion layer is narrower than the CB depletion layer. The reason for the different ...
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Analysis of power amplifier bias circuit: does it need to be thermally bonded?
I'm in the process of building a medium power amplifier for the 20m band (14MHz) and I'm experimenting with bias circuits. The amplifier is a classic BJT push-pull arrangement with a transformer ...
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714
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How does gate-source voltage forward bias the source-substrate junction of MOSFET?
In forward bias, the p-type is connected with the positive terminal and the n-type is connected with the negative terminal.
The junction that I'm observing is the source-substrate junction. The source ...
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NPN BJT Operation - What does it mean for the Collector - Base junction to be reversed biased?
According to this screen grab the Collector Base junction must be "reversed biased". I seem to be confused about the meaning of that. I thought that the Collector needed to be at a higher ...
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CMOS Transmission Gate Body Bias in 74HC4052
Page 2 of the 74HC4052 data sheet shows a diagram of a transmission gate. I'm curious about the way the body of the NMOS transistors is biased. It looks like when the t-gate is off, the body is ...
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Why is the bias input current of an op amp a constant value?
I read this text on op amp input bias current. It says:
The input pins are the base pins of the transistor (or gate pins in the case of FET inputs). In order for the input transistor to operate, the ...
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Node voltage increases in voltage divider
I am planning to use a voltage divider in order to measure the capacity of a group of lithium batteries; in order to minimize power consumption, I biased a common-emitter switch (Q1) with the ...
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115
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How do I bias two OTAs without dividing the current?
I'm trying to achieve automatic gain control in an audio circuit, which requires me to use both diode pins of each amplifier available on the LM13700 chip. The diode pins accept a current (Idiode), ...
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Common Source MOSFET Amplifier Biasing
While reviewing simple transistor amplifier biasing techniques I came across this paragraph in Microelectronic Circuits by Sedra & Smith.
Here too we show the \$i_D–v_{GS}\$ characteristics for ...
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297
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Why doesn't this non-inverting amplifier work with a biased signal in a real circuit?
I have a signal with amplitude of 200 mV biased to 4.5 V. I would like to amplify that signal (AC only, no DC gain) after biasing with a single supply op amp. I have tried a non-inverting op amp ...
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I have a carvin v3m 50watt tube amp head, red plating/bias help
The amp has 4 el84 tubes and 4 12ax7 pre amp tubes, the amp lost about half of its volume and the power tubes are red plating, is there any thing other than the tubes that I should be looking out for ...
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Trouble analyzing biasing circuit
I'm having trouble analyzing this biasing circuit.
It's supposed to shift Vin up by 1.4 V, and everything works when I simulate it, but I can't get anything out of the manual analysis.
I know that ...
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