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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9
votes
7answers
915 views

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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2answers
92 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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3answers
87 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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0answers
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, ...
0
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1answer
55 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) ...
2
votes
1answer
44 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 ...
0
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1answer
65 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"...
4
votes
5answers
243 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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0answers
31 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
203 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 ...
0
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1answer
42 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 ...
0
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1answer
57 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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0answers
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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1answer
160 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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2answers
160 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 ...
1
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1answer
39 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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0answers
70 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 ...
1
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1answer
285 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 ...
1
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1answer
86 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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0answers
100 views

How to calculate neutral base width for an emitter-base junction with forward bias voltage

I am trying to find the neutral base width for an emitter-base junction with a forward bias of 0.75V and a base-collector junction reverse bias of 20V. I am not sure how to factor in the forward bias ...
2
votes
3answers
265 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, ...
0
votes
1answer
73 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 ...
0
votes
1answer
364 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 ...
1
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0answers
72 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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2answers
51 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,...
2
votes
2answers
42 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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3answers
78 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 ...
2
votes
1answer
40 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 ...
2
votes
1answer
56 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
471 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 – ...
3
votes
6answers
525 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 ...
1
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2answers
135 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 ...
0
votes
1answer
220 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 ...
0
votes
3answers
106 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 ...
0
votes
1answer
88 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 "...
0
votes
1answer
37 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 ...
0
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0answers
37 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 ...
2
votes
3answers
136 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? ...
1
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2answers
59 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 ...
0
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0answers
64 views

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.
0
votes
1answer
122 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 ...
2
votes
1answer
183 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 ...
1
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7answers
2k 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 ...
0
votes
2answers
61 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 ...
0
votes
1answer
99 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 ...
0
votes
1answer
184 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 ...
1
vote
2answers
484 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 ...
0
votes
3answers
327 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 ...
0
votes
1answer
76 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
votes
1answer
205 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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