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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26 views

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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76 views

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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407 views

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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95 views

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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68 views

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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38 views

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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34 views

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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2answers
476 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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185 views

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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1answer
50 views

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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2answers
697 views

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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129 views

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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76 views

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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57 views

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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160 views

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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139 views

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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326 views

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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62 views

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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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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120 views

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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119 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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22 views

Single-ended vs differential measurement of high-impedance voltage sources

I'm designing a low-cost multi-channel DAQ device with target resolution above noise of 30-50uV DC and +/-2V range. For this task I've selected ADS1220 ADC ICs: it has a 2.048V internal reference, ...
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1answer
66 views

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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1answer
92 views

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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84 views

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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435 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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43 views

How to protect power supplies and pulser in DC bias + high voltage pulser combined circuit?

I am building an electric circuit in which a DC bias power supply and a high voltage pulser are mixed. I need to save each one from the other with proper safety measures. I have researched several ...
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3answers
307 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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1answer
46 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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1answer
71 views

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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76 views

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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178 views

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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208 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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1answer
55 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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104 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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1answer
453 views

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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1answer
90 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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3answers
311 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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87 views

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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1answer
435 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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74 views

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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112 views

Design of bias-T (L band,10 MHz,DC)

I want to design a bias-T for satellite application where L band RF (950-2150 MHz),10 MHz, and DC will be multiplexed. I need help in finalizing/selecting the inductor(choke) through which DC (13V/18V,...
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2answers
51 views

Biasing network for phototubes and photomultipliers

I have some doubts about typical biasing network for vacuum phototubes and photomultipliers. Precisely, let's start by a simple photocathode. I have seen some biasing network like this one: In this ...
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92 views

Why does the bias decreases in this clamper circuit?

I'm trying to do a positive clamper circuit in easyeda.com to bias a triangular signal of 200mV pk-to-pk at 1kHz centered around 0V. Here's the circuit: The bias seems to work only during the first ...
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1answer
43 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
57 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
756 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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6answers
703 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
173 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
298 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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