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
35 views

Bias T with pulse train

I want to bias my pulser output which is 0 to 30V pulse train. (Which means I want to make 30 to 60V pulses) First, I used a bias T with 30V DC input: I found that it works as a differentiator which ...
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1answer
48 views

How can I find the power provided by the battery?

simulate this circuit – Schematic created using CircuitLab How can I find the power provided by the battery? I've calculated the operation point: Vce(Q1): 8.12V IC(Q1) = 1.63 mA Vec(Q2): 6.25V ...
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2answers
65 views

Source Resistor of JFET Source-Follower

I am designing a simple Buffer to get the voltage of a high-impedanze source to an ADC (60k Impedance). For that I choosed an JFET in the source-follower configuration. simulate this circuit – ...
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7answers
303 views

Why do we need 4 resistors for a common emitter amplifier?

I'm studying the 4 resistors bias configuration, I'm trying to understand why we need everyone of these resistors. If I understood correctly, Re is used to make the Q-point stable, while R1 and R2 ...
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2answers
112 views

How does this BJT biased with a diode work?

I'm trying to teach myself some basic electronics and I'm stuck on understanding what's going on with this simple NPN transistor circuit that is using a diode for bias. I've simulated the circuit ...
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1answer
46 views

How can I choose the resistors for a push-pull class AB amplifier (diode biasing) to get a certain bias current?

Hello guys, this is my very first question. This is a part from a BJt audio amplifier volume control with 3 stages (Pre-amplifier,Buffer, & Power amplifier). This is the power amplifier stage. I ...
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3answers
61 views

Opamp input bias current and current sources

I have a current source connected to a load and I want to measure the voltage at the output of the source, and therefore I would like to buffer this voltage. In this configuration, I am under the ...
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1answer
78 views

How does a transistor work as a switch; internally what actually happens?

I have searched about this, and wherever I see they mention two things: How [the transistor] will be biasing Q-point must be at the cut-off and in saturation. But I want to know in the case of the "...
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1answer
21 views

Bias Input Current Compensation for Instrumentation Amplifier

What is the motivation to choose R1=R5=5k6 Ohm? If they are for bias current compensation and both OP Amps have same Bias input current, 10k should be taken in my opinion to eliminate common mode ...
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35 views

BJT conceptual doubt

I was given this problem in a problem set. I want to ask what will the voltage at Base when \$ \beta \rightarrow \infty\$. My answer to the problem - When \$ \beta \rightarrow \infty\$ then width of ...
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3answers
126 views

Common emitter with input connected between the voltage divider and base

Similar questions have been asked before, however they don't really answer what I'm actually looking for so I asked a new question instead. TL;DR Why does the circuit below cause noise at the output? ...
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0answers
24 views

Vbe multiplier current sense controlled

Using a classical amplifier output stage (whatever it is), is there a Vbe multiplier (rubber diode bias circuit) that allows you to adjust the current through the sensing of the power resistor of the ...
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2answers
42 views

maximum collector-emitter voltage in BJTs

I am reading BC817 datasheet. According to the datasheet, maximum collector-emitter voltage at open base condition is 45 V. In typical applications we don't use open base configuration. My question is ...
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BJT voltage divider bias problem

Hi I am having trouble with how to find Req of the resistor network of the bjt circuit on the schematic. How can I calculate it to find Ib Vb values? thanks.
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1answer
97 views

Reducing the number of expensive capacitors in an audio opamp circuit

I'm designing a guitar effect (simple booster) which uses a CD4053 cmos switch as outlined here (http://www.geofex.com/Article_Folders/cd4053/cd4053.htm) As you can see from the second diagram, RG ...
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1answer
92 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
970 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
52 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
91 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
50 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
206 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
40 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
127 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
62 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 ...
2
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1answer
87 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
50 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
63 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 ...
2
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1answer
64 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
33 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
100 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
134 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
791 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
143 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
148 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
150 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
337 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
86 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
116 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
100 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
154 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
58 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
206 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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0answers
56 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
95 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
469 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
56 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
57 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
1k 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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