Biasing is establishing predetermined voltages or currents at various points of an electronic circuit for the purpose of establishing proper operating conditions in electronic components. Many electronic devices whose function is processing time-varying (AC) signals also require a steady (DC) current or voltage to operate correctly — a bias. The AC signal applied to them is superposed on this DC bias current or voltage. The operating point of a device, also known as bias point, quiescent point, or Q-point, is the steady-state (DC) voltage or current at a specified terminal of an active device with no input signal applied. A bias circuit is a portion of the device's circuit which supplies this steady current or voltage.
Questions tagged [biasing]
193 questions
22
votes
5 answers
Effect of bootstrapping in amplifier circuit
I am trying to understand this "bootstrap bias" amplifier circuit. The picture below is adapted from the book "Transistor Techniques" by G. J. Ritchie:
This circuit is a variation of the "voltage divider bias", with the addition of the…
favq
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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 created using CircuitLab
But then, while staring at, it I…
Trevor_G
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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 below) and it immediately impressed me.
(The picture is taken…
Circuit fantasist
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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 pulled to ground "enough" - only going 12V then to…
MattyT2017
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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 and Q2, so that Q1 would conduct only positive…
Keno
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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 easier than i supposed to manage. I have now a…
lastime
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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 phenomenon?
lub2354
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7
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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 base current (IB) must flow. This base current is…
S. Rotos
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7
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Push-pull power amplifier on complementary darlingtons
I decided to make a power DC-amplifier. I used complementary darlington pair TIP142 and TIP147. Also TL082 used for negative feedback. The schematic is as below:
I gave 100 kHz sine signal and under oscilloscope I noticed the crossover distortion.…
Madras
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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 switch on?
Enrico
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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\$ (which is the reverse saturation current of…
A6EE
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4
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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?
imran muhd
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4
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4 answers
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 voltage Vce also increases in saturation…
Nitish
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1 answer
How are the PNP transistors biased in this microphone circuit?
If I am not wrong, the biasing voltage to turn on an NPN transistor is emitter voltage + 0.7 volts.
Similarly, the PNP biasing voltage is emitter voltage - 0.7 volts.
Can someone explain how the two PNP transistors at the XLR input are biased? A…
Vijayendra Kumar
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Darlington biasing design error in a commercial frequency counter oven control circuit?
I am repairing a commercial frequency counter (brand to remain anonymous) that had the crystal oven visibly overheat. There is a small PCB in the oven that holds the crystals, the oscillator circuit, four diodes connected in series whose voltage…
LevelUpEELab
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