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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How to determine the bias point for Class C power amplifier

I am designing a class c amplifier as a part of a doherty amplifier at 3.5GHz using GaN HEMT. I wanted to know how do i bias the transistor in class c region. I know the bias point should be in cutoff ...
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How can KCL be satisfied here?

In the transistor biasing using diode below assume that at time t1 the circuit is stable and apply KCL at the junction of the three devices you have: ...
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How to find the Diode voltage in forward-reverse bias combination circuit?

This circuit contains forward and reverse bias. The question is to find Vd and Id. In this case, my understanding is that the current from the leftmost mesh will not flow to the middle and rightmost ...
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LNA circuit: why is the inductor causing a voltage and current drop?

I am designing the following circuit whose schematic and testbench I put below: I performed a DC bias analysis. Theoretically, I would expect that at DC the inductor would be a short-circuit and the ...
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D/C Decoupling Capacitor for Microphone Bias

I have the circuit below which provides a bias voltage to a microphone: C10 is listed as a 47uF (bipolar) capacitor Is there any reason I can't use something like a 100nF bipolar ceramic instead?
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Offsetting an ultrasonic receiver's signal for an amplifier with a floating ground

I have an ultrasonic receiver that I'm putting through an amplifier. I've created a floating ground for the amplifier (because I want to pretend having a negative voltage supply). However, to achieve ...
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5 answers
178 views

Measuring bidirectional voltage drop across current shunt on positive rail

I want to measure a voltage drop across a current sensing resistor (in both polarities) on rails up to 30V using an Arduino / AVR ADC with 1V1 reference. For background, this is a part of a battery ...
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Bias supply of forward converter: Startup circuitry component selection

The bias circuitry of a forward converter is shown below. Iam unable to follow the derivation of start up resistor values( Rstart) given in datasheet: As per me, \begin{equation} R_{start} < \...
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How to use the button on a headset?

I want to implement push to talk on my custom PCB. I apply a 2V DC bias on the microphone line of the jack through a 2.2k resistor. While pressing the button of the headset I see the resistance ...
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Add Voltage Bias/Offset to 2nd-Order Sallen-Key Highpass

I need to add a highpass filter between a signal source and an ADC to get rid of high-amplitude low-frequency signals that would cause clipping. I built a second-order Sallen-Key filter and the ...
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How to drive high side Pmos buck converter at 40+ voltages

I'm working on a buck converter that will have an input of 42V to 80V, switched at 200kHz with a max load of 5A. My load will require a duty cycle range of 75% to 100% I know the componenet selection ...
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Thermocouple bias with LTC2053

This LTC2053 application note shows a thermocouple bias using two 10 MΩ and two 1 MΩ resistors. I understand the idea that the power supply is divided by two 10 MΩ resistors for good common mode ...
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Biasing a transistor with a Zener diode (calculate R)

I am trying to have a stable output voltage (12V) for the power supply that is changing between 28 V- 150V: simulate this circuit – Schematic created using CircuitLab I checked the datasheet of ...
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Class AB power amplifier from "Electronic Devices" by Thomas L. Floyd

I am an electronics engineer. I work as an industrial automation engineer in industry. As an electronics engineer, I love amplifiers and other stuff. I was reading Electronic Devices by Thomas L. ...
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A question related to a NPN transistor having a DC bias

β = current gain I made the circuit of the above picture with LTspice. (A graph of Vce) (A graph of Vbe) And I was able to get 4.2966V for the value of Vce and 0.6543V for the value of Vbe. However, ...
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2 votes
2 answers
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What happens when you reverse bias a NMOS with separate body terminal?

I am trying to create a current limiting circuit with minimal output capacitance. I'm trying to build a circuit that optimises low parasitic output capacitance over linearity. I used a SST215 DMOS ...
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FET Simulation DC Gate Voltage Different for VDC and VPULSE

While simulating a basic common source JFET amp I found that eliminating the input capacitor improved the gain of the circuit dramatically. This is because without the input capacitor, the gate ...
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Forcing the bias current of a voltage feedback amp into a larger Class AB by a resistor

Can I force any voltage feedback amp to flow current in one side of its output stage (therefore moderate over-biasing it to work in an extended class-AB area), by simply connecting a power resistor ...
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2 votes
2 answers
605 views

Why are pull-up inductors biasing the power amplifier output of radio transmitters chips needed?

I have seen many designs where the antenna/PA output is fed DC voltage through an inductor. Why not leave it out and feed the DC bias directly? It is L1a in the diagram below: There are some values ...
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Explanation about op-amp bias resistor and bootstrapping

I am reading a book on op-amp and its applications in linear-integrated circuits and came across this topic of creating an op-amp circuit with very high input impedance. I believe that I understand ...
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1 answer
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DC bias differential amp for unipolar power supply?

The PCM1793 datasheet has a filtering and amplifier stage. I built this without realizing that it requires a bipolar power supply. I'd like to get it to work with a unipolar power supply. I don't have ...
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4 votes
2 answers
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Where does one find the minimum voltage above the negative rail an op-amp can output in their datasheets?

I was planning on using a UA741CP (from TI) as a differential amplifier (to get a current value from a shunt resistor and then administer that value to the ADC of an MCU to avoid noise). However, I ...
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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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1 answer
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DC bias for AC measurement with an Arduino

I'm trying to make an AC and DC voltmeter with auto-ranging and auto-switch (between AC and DC.) The maximum input is 0~24VDC and -24V~24VAC. I've built a voltage divider with some optocouplers ...
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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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Input bias current and offset current calculation for an LM741 op-amp

This is my circuit diagram: The bias current of the LM741 op-amp is 80nA. The offset voltage is 1mV. The LM741 has relatively large current offsets, voltage offsets and input bias. I calculated the ...
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How do I add a DC offset to my RF signal for a 50 Ohm Device?

I'm working with a system that requires a ~250-400 MHz modulation signal from 0 to 1.5 V (or -1.5 to 0 V) on an electro-optic modulator (EOM, Jenoptik AM635). I have a signal generator capable of ...
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5 votes
2 answers
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How to bias a MOSFET class AB amp?

I'm working on a class AB amplifier that is used to either source or sink current. The reason for using MOSFETs is space constaints and that high power BJTs are only available in large leaded packages....
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Non-Inverting OpAmp Bias not acting as expected- UPDATE

I have been experimenting with an opamp as a noninverting amplifier for a Piezoelectric vibration sensor 0-1Khz expected. I am only interested in the positive portion of the signal as an average hence ...
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9 votes
7 answers
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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 ...
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How to derive transfer function for DC feedback coupled transistors?

I am not sure where to start deriving the transfer function of this circuit. If I do a control diagram then I need to know the initial values to convert the system into the Laplace domain, so I guess ...
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3 answers
168 views

\$R_e\$ when using a common collector amplifier

For the DC biasing of a common collector BJT amplifier, how to choose \$ R_e\$ to get a proper DC biasing? (see image attached). Furthermore, is it possible to control \$V_{ce}\$? I am confused. ...
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How to calculate bias resistor values to drive IR diode

I'm creating a circuit to do communications via a digital serial infrared link. My requirements are for the link to support relatively high speeds (maximum serial bit rate is 4,000,000 bps or 4Mbps) ...
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2 votes
1 answer
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Bias T for modulation of VCSEL laserdiode

For my project, I would like to design a Bias Tee for a VCSEL laserdiode, because a modulation is required. The bandwidth is 20 KHz - 10 MHz. My steps are shown below: As a reference, I have used the ...
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1 answer
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Why do we generally add capacitors in series with AC sources when DC also exists in the circuit?

This is probably a noob question but, essentially, why do we often place capacitors in series with AC signal sources? I understand that we sometimes want to isolate the DC signal to "its own"...
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4 votes
5 answers
611 views

Accurately amplifying a number of current sense transformers

I've got 16 current sense transformers that are being used to monitor AC loads. The SCTs are current output type, producing 50mA on a 100A load. The maximum burden resistance is 10Ω, thus the voltage ...
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2 votes
3 answers
412 views

Inverting Amplifier Not Applying Gain to Bias Voltage

I am simulating an inverting amplifier circuit (Page 3 in this app note) with LT spice. The amplifier has a gain of 10 V/V and since I am using a single rail supply, I am applying a bias voltage at ...
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1 answer
68 views

How should I find the DC bias values for this circuit?

I would like to build this circuit, but I have to find the DC bias points first. Based on current requirements of total 11mA, I decided to set current through the differential amplifier stage to be ...
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1 answer
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Do touchstone (s2p) files for capacitors from include the ESR/ESL, or do I need to add an ideal R/L for simulation?

Manufacturers like muRata and AVX provide .s2p files for their RF capacitors. When modeling for simulation in my EDI software, do I need to include the ESR graphed in the datasheet for the frequency ...
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Understanding MOSFET operating transitions

I'm trying to conceptually understand the output voltage and the operating condition transitions that the MOSFETs in the circuit below go through as the input voltage is swept from 0 to VDD. It's not ...
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1 vote
1 answer
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Gate voltage range - Biasing circuit

I am looking for Biasing circuits which can provide gate voltage in the range of -4V to -0.5V. In the application note of AMPLEON AN-11130, there is a table mentioning the specifications of the ...
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1 vote
2 answers
277 views

Choosing the right opamp for biasing a square wave

I am trying to bias a 1MHz, Vpp = 1V, bipolar square wave signal coming from an opamp. I want to bias it by 1V, the 1V bias (Vcm) is available at an ADC's output port. I am thinking about using this ...
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1 vote
1 answer
79 views

Please explain negative bias and "a stronger field to sweep carriers out of depletion"

I want to understand what a comment means, and I couldn't ask in a comment. In this question, someone asked why use an op-amp with a photodiode rather than just a resistor. The answers and comments ...
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133 views

What is the correct way to bias a floating instrumentation amplifier?

Im designing a voltage measurement circuit that needs to measure differential signals in the order of mV in the presence of high voltage common mode noise. Im using a isolated DC/DC converter that is ...
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1 vote
1 answer
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Where do input bias currents flow and what voltage drops do they create?

I have asked this question (and answered it below) mainly as a continuation of the question, How does the compensation resistor in an inverting amplifier compensate for the input bias current?... but ...
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1 vote
1 answer
94 views

Single supply amplifier biasing

I'm trying to understand this circuit. I can see that BW1 is a low pass filter and BW3 removes any DC from the output signal, but what does BW2 do? If it is acting as a filter, is it a high pass ...
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2 votes
3 answers
348 views

Suitable bias resistor for microphone with higher voltage source than microphone's rating

I have headset microphone with a rated impedance of 2.2Kohm, that according to the data I've been able to find for it can be powered by 1.5 to 10v. I do not know what the maximum current is, ...
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1 answer
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Does the bias amplifier of the RLD amplifier need to be connected to reference electrode of the measurement sensor?

I am using the MyoWare AT-04-001 muscle sensor and FSR400 force sensing resistor sensors with the ADS1299 amplifier and ADC and I need to improve the CMRR. The datasheet mentions that an RC filter ...
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0 votes
1 answer
469 views

Biasing circuit - Voltage follower circuit

I am using MABC-001000-DP000L, which is and Bias controller/sequencer. I am using this for Providing gate voltage and drain voltage to the power amplifier. In the datasheet, it is mentioned that the ...
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1 vote
0 answers
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Biasing circuit schematic - MABC-001000-DP000L [duplicate]

I am trying to design a bias controller circuit using MABC-001000-DP000L. I am unable to find the full schematic of the same. Has any one used MABC-001000-DP000L for designing bias circuit? Edit:- I ...
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