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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1answer
51 views

Why are there three transistor pairs in Class B Power Amplifier circuit?

I have a Class B amplifier circuit to be done in lab. Why three pair of transistors are used in this? I suppose one is a Darlington pair but what is the requirement of the third one. Also, why there ...
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7answers
652 views

Emitter resistor and biasing voltage

In many articles regarding transistor biasing I see a circuit like below and I don't really get what is the point of biasing like this WITHOUT emitter resistor Re? When emitter branch is connected ...
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2answers
47 views

How to bias an AC signal correctly?

I have an AC signal and want to give it a new DC offset. There are some questions about my experiment results. (The original signal bias and terminal output bias are the same because I want to know ...
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1answer
82 views

Stuck on designing a simple CS Amplifier

I am trying to design a common source amplifier and getting stuck during the design process. Was wondering if anyone can help me out. Ill show my process with comments and if anyone can show me the ...
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1answer
34 views

Autobias Vbe with output current sensing

this is a question about analog audio amplifiers and automatic regulation of the output stage bias circuitry. I basically need to implement an autobias circuit on this output stage topology: As you ...
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2answers
95 views

Howland current source with voltage reference [closed]

I need a precision current pump for small ac signals(50uA) and i tried it in multisim with a howland topology. It works however i need the load to not be grounded but bound to a bias voltage. Here i ...
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0answers
39 views

RF GaN transistor biasing

I am trying to understand the difference of pulse operating. How I get there is two ways. For example. Bias procedure: Set \$I_D\$ limit to 400 mA, \$I_G\$ limit to 4.5 mA Set \$V_G\$ to -5.0V ...
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2answers
85 views

Sampling a +/- 12v signal with a 0-3.3v micro pin

It's been ages since I've had to use my old school notes. I am trying to get an esp32 to read an analog voltage that ranges from -12 to +12. Obviously, the 3.3v esp32 won't like those voltages so I ...
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1answer
53 views

Applying Ripple to a DC Source?

I have a system that is powered by a 25V Lithium ion battery pack. I need to test the system with a 1 Vpp sine applied on top of the 25V supply, so 25V +/- 0.5V ripple. I know theoretically to get ...
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1answer
31 views

Active RF Antenna power PCB layout: where to place the inductor for a bias tee?

I have an active RF antenna that is powered through an inductor in a bias tee network. How should I draw it on PCB layout? I have 3 ways to do that. In these layouts, up is capacitor, bottom is ...
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1answer
44 views

How to calculate current sink

Below schematic is what I have on the breadboard: simulate this circuit – Schematic created using CircuitLab R1 is there to sink 10mA of current to bias LM317, but 470 ohm is a value that I ...
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1answer
61 views

Bias voltage of transistor [closed]

I would like to understand the purpose of biasing the transistor and why It has to be halfway between Vcc and ground? And which terminal of the transistor (Base, collector or emitter) should be ...
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1answer
41 views

What does Bias Repeatability tell me in an IMU's spec sheet?

If there is a standard interpretation of bias repeatability as it applies to a gyroscope, what is that interpretation? This document indicates that it represents the average change in bias between ...
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1answer
31 views

Forward and Reverse Bias regions for voltage versus current of diode

Below I have the graph of the voltage of a diode versus its current. As you can see, the forward bias region is when Vd>0 and reverse bias when Vd<0. My question is: In which region does Vd=0 fall ...
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2answers
88 views

Reduce minimum operating voltage of an H-bridge

I have purchased the following H-bridge and I'm controlling it with a microcontroller: https://www.amazon.com/H-Bridge-Brakes-Forward-Reverse-Full-Duty/dp/B07GFFVZKS My problem is that the MOSFETs ...
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2answers
85 views

JFET Vgs Calculation Equation

Does anyone know the formula to calculate the Vgs of a JFET used as a variable resistor? Say, I have a Vds of 24v and I require a current of 20mA (just arbitrary values) I would need a 1.2k resistance,...
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5answers
1k views

Isolated audio without a transformer

I'm putting together a guitar pedal for splitting the signal to two different amps. One of the features I want to put in is a 'ground-lift'; isolating the signal to avoid ground loops between the two ...
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3answers
404 views

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'...
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2answers
135 views

Several questions on video circuits

Part 1: Looking into several old good home computer video output circuits I see the similarity I can not fully understand. They use diodes or transistors as a bias for the final output section. See ...
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0answers
105 views

Applying a 1/3 bias to an LCD display spec'd at 1/2 still safe?

We're currently using an MSP430 with an integrated LCD controller that only has a 1/3 bias mode. The LCD display has a 2-mux configuration and the data sheet specifies "drive method: 1/2 duty, 1/2 ...
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1answer
95 views

Presence of Crossover Distortion in Class A Amplifier

This question is about theory facts of class A audio amplifier. It is known that class A amplifier is usually biased so that an amplifier's quiescent point is in the middle of the amplifying device's ...
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3answers
1k views

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 ...
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1answer
161 views

How to Model a Bias Tee in ADS

I'm modeling a Bias Tee in ADS and I wanted to ask how to add board parasitics into the model and what should the results of a good model look like in terms of the S-parameters. This is my first time ...
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0answers
61 views

How to bias an AC input composite video signal [duplicate]

This is a question about biasing 0V-referenced AC input signals to a positive single-ended signal. Even if the best solution for my question would be something else (and I'd like to hear about that, ...
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1answer
91 views

Cascode Amplifier Biasing Sequence

I'm trying to understand the proper biasing procedure of a cascode distributed amplifier part that requires three power supplies. A positive drain-source VDD, a negative gate-source VGG1, and a second,...
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1answer
70 views

Lower noise in biased op amp

I have a circuit similar to this. I’m trying to lower my noise under 60 Hz. Using pspice I keep finding that I need a very large resistor for R5, like 50 gigs but in practice this is not giving me the ...
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3answers
113 views

Audiable pops when switching DC biased audio signal

In my previous question, I have asked how to DC bias audio signal for a crosspoint audio switching matrix (Switch array (crosspoint) and DC biasing of audio signal). I am using the following circuit ...
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2answers
54 views

What bias voltage is applied to a PIN photodiode when connected only to multimeter

If I take just a PIN photodiode (e.g. BPW34 FAS ) and connect a multimeter to its terminals to measure current, for example: expose the photodiode to the sunlight and read current of ~1 mA on the ...
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2answers
100 views

Input Bias Compensation Resistor Calculation for an Integrator

I have been reading the following tech note from Analog Devices that discusses designing an op amp circuit to compensate for the input bias current: https://www.analog.com/media/en/training-seminars/...
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40 views

What would be the difference in the voltage transfer curves of this two circuits, assuming the op-amps are not ideal?

How does the resistor connecting the non-inverting terminal to ground affect the transfer curve?
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2answers
74 views

Single Stage Amplifier CMOS - Biasing Issues

So this is kind of vague question. I'm wondering what the approach to biasing MOSFETs in saturation is. For the following circuit, I really have no specifications - I'm just trying to play around ...
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1answer
374 views

Driving a butterfly package DFB laser

I want to drive a DFB laser in a type-2, 14-pin butterfly package. The manufacturer has provided limited information on how to bias the laser diode and could not get any information on the reference ...
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0answers
55 views

How to solve practical OPAMP with finite differential resistance and finite offset current while other parameters can be considered ideal?

simulate this circuit – Schematic created using CircuitLab Ip(bias)=200nA rd=differential resistance=5Mohm a=infinite What should be its output? I am confused if I should consider negative ...
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1answer
49 views

How does the spectral response of a photodiode change with bias voltage?

Look at this data sheet, in the second page we have a graph for the spectral response. Now, I have learned that photodiodes must be reverse-biased in order to get a decent signal from them, but then ...
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1answer
514 views

Inject 5V bias power (“fake” phantom power) for microphone (ModMic)

I've recently bought a ModMic4 for my PC, but the signal level is very low and have to amplify it quiet a lot digitally, which introduces ton of white noise and I have to use noise supression which ...
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3answers
83 views

Behaviour of Voltage on Base in a fixed BIAS Common Emitter Amplifier

I'm having some trouble understanding the behaviour of the basic common emitter fixed bias amplifier. I've been looking at this for awhile now and I'm starting to think there is a foundational ...
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2answers
302 views

In an AC coupled Op-Amp circuit where do input bias currents flow from?

If we have an AC coupled amplifier like the one below, i've read and been told it needs a DC path to ground to allow input bias currents to flow, though I just can't get my head around this, I bias is ...
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2answers
72 views

making a photodiode module

I am trying to do stimulated Raman scattering microscopy. In this experiment two pulsed laser beams are used . The wavelength of these two laser beams is tuned to match a specific Raman frequency of ...
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1answer
50 views

Basic questions on biasing

I have some trouble understanding a basic concept. Here is my question. This is from a document which can be found on the website, http://www.ti.com/lit/ug/tidu765/tidu765.pdf The text ...
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1answer
38 views

If positively biasing amplifier does minimum voltage on input pins apply?

I am using an amplifier to bias a signal for an ADC. The signal range is -1.25 to 1.25 volts. I have the 2.5V precision reference for the ADC through a voltage divider to the inverting input of the ...
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1answer
62 views

Why is the source voltage 1/4 of the supply voltage applied to the drain in a voltage-divider JFET circuit?

According to a Junction Field Effect Transistor (JFET) article in ElectronicsTutorial, the voltage across the source resistance is equal to 1/4 the supply voltage applied to the drain/gate for a class ...
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1answer
417 views

when a diode is forwards biased can current flow backwards through it?

when a diode is forwards biased can current flow backwards through it? this question comes from me trying to understand class AB amplifier biasing, so any additional comments about the diodes' use ...
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1answer
68 views

Bias resistor in opamp circuit

For the circuit below, what is the purpose of the 2 bias resistors. They are said to detect breaking, what does it mean.
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1answer
776 views

How to bias(voltage offset) unity gain buffer

First post so sorry for any bad formatting. I'm trying to figure out how to bias my signal going through a non-inverting op amp with a gain of 1. Because I want a gain one just 1, it would just be a ...
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1answer
51 views

how to adjust drain bias to keep power dissipation constant (HEMT)

I am reading a chapter in a thesis about using HEMT (high electron mobility transistor) as a cryogenic amplifier. The measurement scheme is to use the gate voltage fluctuation's influence on the drain ...
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2answers
123 views

Understanding of class-AB currents

I am trying to understand a simple class-AB output stage. The bias voltage for the transistors is made by using two diodes. The following picture show the circuits. The currents drawn are how, i ...
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2answers
174 views

Need help to increase schmitt trigger sensivity in a circuit

I need help on a circuit I've designed to detect hits on a piezo sensor on a drum. It uses an opamp with 2 channel, on goes to a schmitt trigger, the other to the ADC input on the XMEGA ...
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3answers
562 views

Gilbert cell biasing

I'm new here so I'm going to make is as simple as it can get.. How can I bias a Gilbert cell with bjt transistors like this one: What methods can I use to bias the transistors? Is there any example ...
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2answers
103 views

how can I get leakage current in tlp?

I got tlp test data and found that the current at vertical line means leakage current. But I don't understand the method how does the tlp-test measure the leakage current. I tried to search the ...
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1answer
40 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 ...