Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [bias]

A DC voltage or current in a circuit to set the operation point of an active or non-linear component.

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What's input bias current in opamps?

Is it the current you have to drive in the input to get a specific, defined voltage at the output? And don't the currents cancel each other when applied to both inputs?
Federico Russo
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DC biasing audio signal

I have seen a few different ways of adding DC bias to an audio signal. I have simulated them and they all give me similar results, but I can't figure out why choose A over B or C. My audio source will be a Line Level Audio -2V to +2V AC passed…
jsolarski
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VBE Multiplier with Emitter Resistance Cancellation

Function of shown circuit is biasing of output power stage complementary audio amplifier. P1 allows precise adjustment of \$ V_{CE} \$ of VBE multiplier and \$C_B\$ improves its rail rejection. \$ r_e' \$ negates unwanted effects of \$ r_e \$, also…
Keno
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Input coupling to Class AB amp with diode bias. One capacitor or two?

When AC coupling the input signal to a Class AB (Push-Pull / Complementary Pair) which is diode biased I see two different approaches: Signal connected between biasing diodes with single decoupling capacitor: Signal connected directly to each…
Frosty
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RS485 termination: AC + failsafe + parallel + bidirectional

Knowing that I need to refine my RS485 circuitry, I've been reading. I have a series of specific questions and I hope that you'll indulge me as I describe how I attempted to follow through an application note. Here are some basics of the serial comm…
Reinderien
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Are film capacitors affected by DC bias?

After looking around, I have found quite a few things about how DC bias reduces effective capacitance for a ceramic, or electrolytic capacitor, however nothing seems to talk about the effect on film capacitors. I've found a couple of papers about…
Puffafish
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What is the advantage of gate resistor (R3) in this JFET voltage divider biasing circuit?

I've been studying and building JFET circuits to serve as a high-impedance input to a DIY guitar amp. In my research on voltage divider biasing, I've come across a circuit in Nuts & Volts Magazine that has me perplexed. It's shown on the left in the…
Dave H.
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Effective capacitance of a capacitor under DC-bias voltage

In my system, I charge a multi-layer ceramic capacitor between 3 V and 5 V using a buck converter. Once the voltage reaches 5 V, the capacitor starts discharging until it reaches 3 V, and the cycle repeats. However, I require the capacitor to have a…
shakingwindow
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Why is the collector feedback bias popular in electret-mic preamp circuits?

I got some simple electret microphone modules and I've been experimenting with audio amplifiers. I googled to find some example circuits, and I found that most of them resemble the circuit above. I built this one and it works fine. If I'm not…
S. Rotos
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Pre-biased Bipolar Transistor (BJT) Tradeoffs

If you go to the Discrete Semiconductor category on Mouser.com, there is a section for "Bipolar Transistors - Pre-Biased". Is this as simple as including a resistor in series with the base? Are there other nuances about this type of package?
Anton
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How to amplify electret microphone to range from 0-5V with bias of 2.5V?

I'm new to op amps and have tried many circuits but don't get the results I expect. I know I must do some math but I get so confused. I thought my question is really simple but it turns out it's not. I just want to amplify an electret mic to 5V.…
Roelf Daling
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Bias analysis in a dual BJT circuit with feedback

I am building an Wooly Mammoth audio circuit, and I am really interested in finding how and why it works. You can check out and simulate the whole thing here. I must say I haven't been able to get any valuable result from simulation. It provides a…
Serge
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Why are multiple bias voltages required to drive an LCD?

I have read this document: AN658 - LCD Fundamentals and the LCD Driver Module of 8-Bit PIC® Microcontrollers I understand that the main concern is to maintain 0 VDC bias on every pixel when driving an LCD display. I do not understand why there are…
Chupacabras
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What is the purpose of a bias resistor?

Could someone explain what "bias" is. And why do some devices need an external bias resistor?
Toby Jaffey
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Is there any advantage to biasing a transistor with a zener diode rather than a (resistor-based) voltage divider?

In the figures below, we see two methods of biasing a bipolar transistor: the first uses a voltage divider, and the second employs a zener diode regulator. Since the voltage regulator appears far more frequently, I'm wondering if there exists some…
seertaak
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