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 is the purpose of these passives in a microphone pre-amplifier circuit?
This is the typical application circuit of the MAX4466 "microphone preamplifier" op-amp.
Are these resistors/capacitors purely for generating a bias voltage? If so, aren't there much simpler ...
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PNP: What happens if the base voltage is higher than the emitter voltage?
Can a PNP transistor switch a 5 volt load such that in the off state the base is supplied with 12 volts and the on state is pulled to ground (Vb > Ve)?
I remember hearing that the base voltage ...
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Op-amp current values
In this App note, page 7, example 3, can someone tell me from where the values for IBN and IBI are coming from? I.e.
\$I_{BN}\$ = -(5 nA + 0.5 nA)
\$I_{BI}\$ = (5 nA - 0.5 nA)
I'm using this MCP601 ...
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Ideas why this operational amplifier could have worse bias stability than anticipated
Background
Below is the simplified schematic of an operational amplifier I tested. I left out compensation components, because the question is about the DC behavior only. The design has sufficient ...
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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 ...
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Bias tee in Vector Network Analyzer
Can I use a bias tee in the back of a VNA (E5080B) as a port 1 and 2, or do I need a mixer for it? I want to measure the network parameters of a device that requires bias.
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Why are the op-amps' positive inputs getting biased to -3.8 V in this differential probe circuit?
My students built a differential probe circuit, basically following this circuit from Hackaday shown below:
For U1 and U2 they instead used MAX4104ESA+ op-amps. The op-amps are supplied through +/-5 ...
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Importance of DC blocking capacitor type when we don't care about audio quality
I am working on a board design which is very limited in space. I am taking input from a passive guitar pickup and sending it through a high impedance buffer op-amp, a low pass filter, and then a non-...
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2
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Coupling floating differential inputs to an amplifier with/without resistor pair
My question is about wiring a "floating differential input" signal to an instrumentation amplifier.
I've read that in the case of a floating signal two high value resistors are used to ...
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Topology of a non-inverting op-amp with bias
I have been trying to decide the best single-supply non-inverting op-amp topology to use the ADC of an ATmega uC for capturing the signal coming from SCT013-030-0-30A-0-1V split-core current ...
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How to bias and obtain dual rail for an IC and do coupling in this case?
Following is a made up example just to make the question clear:
In some cases when using an IC, it requires dual supply for its rails. And in that case such as above circuit, if we had single supply ...
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Bias circuit on memory data lines
simulate this circuit – Schematic created using CircuitLab
I have the above in a vintage computer project's schematic, without specification of the transistor or the diode. The Intel 4289 serves ...
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What should be the signal levels when recording a tape cassette?
I make a DIY cassette recorder from a cheap cassette player. I successfully made a stereo playback circuit that works with recorded cassettes, but I'm having trouble with recording; after recording, ...
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Why is the voltage gain in a fixed bias circuit not the same as l calculated?
In this circuit below: ( I simulated in Multisim )
I measured the DC response in simulation as:
Ic = 3.73 mA
Ib = 15.7 uA
Vc = 11.3 mV
Vbe = 824 mV
I ...
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Biasing a low AC voltage for input to an ADS1115 ADC
I have an AC signal from a position sensor that changes between -200 mV and 200 mV, something like 400mV peak-to-peak.
I have ordered an ADS1115 breadboard and I use an STM32 microcontroller.
I'm not ...
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Finding the Q-point of a transistor: disambiguation
I find the definitions of Q-point that I have been given in class to be a bit ambiguous, so please read on and confirm or correct my understanding.
As I understand from this SO answer, the Q-point or ...
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Is there something wrong with the op amp circuit in this Element 14 YouTube vid?
The video is here with schematic at 3:20 and attached below.
There is no DC path to the non-inverting input, and the only DC route to the inverting input is via the output.
In fairness to the ...
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Compensation pulse for plateau through bias-tee
I'm sending a series of square pulses through the RF side of an homemade bias-tee (R = 1e6 Ohm, C=0.1uF).
Unfortunately, my experiment requires that some of those pulses have plateau time longer than ...
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0.5v bias on a clock pin? [closed]
To verify that I've soldered a pin correctly, I took a scope capture and noticed there is a ~560mV high bias. This is on an old motherboard where one or more capacitors could be bad. What is a good ...
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Biasing a DIY current feedback opamp
For a personal project, I'd like to make a discrete current feedback opamp. Here's a simplified schematic:
The question is about how to bias Q3/Q4.
For a nice class-AB output, the sum of both Vbe's ...
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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
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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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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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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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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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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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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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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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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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3
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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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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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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 ...
user115914
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\$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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