Questions tagged [diff-amp]

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4answers
72 views

Subtractor op-amp configuration to find the diference of 2 signals

How can a differential op-amp be configured in a way that it doesn't amplify but only takes the difference between the signals at the inverting and non inverting input?
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0answers
25 views

What is the difference between galvanic skin response and skin resistance of human skin?

I know this is not related electrical directly, but op amps and Wheatstone bridges are used in these applications. I have seen, Wheatstone bridges with a differential amplifier are used in skin ...
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1answer
42 views

Differential Amplifier - Active Load Current MIrror Logic

I'm trying to wrap my head around the workings of a differential amplifier when a current mirror is used as an 'active load' With reference to this Youtube video leecture: here My understanding so ...
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2answers
142 views

Why need to separate the path of the current of these two signal source?

This is a differential amplifier with common-mode signal as input (figure a) : Since equal voltages vin(CM) drive both inputs simultaneously, there is almost no current through the wire between the ...
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0answers
40 views

BJT Differential Amplifier with active load Analysis

I completed the theoretical parts of DC and AC analysis. I want to test them with the simulator. Both DC and AC analysis failed. I killed DC sources in the AC analysis section and I short-circuited ...
1
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1answer
94 views

BJT differential amplifier

Is there any reason why the gain of a single ended input BJT differential amplifier, with one Rc, is a good approximation of the value of Adm for a common mode input. The simulation shows the ...
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0answers
39 views

Rectified DC current measurement using shunt or Current Transformer

I am working on a project to design a controller for battery charging solution. A 3 Phase delta power (440 Vrms ph to ph) is given to a 3-phase Variac Transformer ( Variac is operated ...
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2answers
61 views

Multiplying oscillator signal with a pulse

I am trying to multiply my oscillator sine signal with my pulse. But, the voltage of the oscillator is too big so it saturates. This is the output I am getting from my oscillator. I am getting the ...
1
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1answer
88 views

Floating Differential measurement?

Can I simply hook up an opamp inputs, (either using a differential or in-amp topology that is/are also powered from a floating power supply), across a device under test that itself has exceeding ...
1
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1answer
32 views

MOSFET Differential Amplifier Bode Plot

I've created a MOSFET Differential Amplifier in PSpice, the schematic of which I've attached. However, when doing an AC sweep and adding a trace to do a Bode plot, the graph is a flat line, and I don'...
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0answers
31 views

Diff Op-Amp in current measurement ignores input [duplicate]

I'm working on a small project which involves current measurement. I'm using R10 to measure Voltage drop (100 mV) when 10 mA current goes through it. Next I'm amplifing that signal around 37 times ...
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2answers
60 views

Differential amplifier with a current source

How to change the current source in the emitter here, so that the whole thing can be biased from a positive power supply (without the need for negative rail Vee) keeping all the other parameters more ...
0
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1answer
65 views

What is an RC time constant and why do I have to wait for the capacitor to carge up before taking samples with ADC?

I am using LTC6403 in my project. It is used for single-ended to differential conversion, which will be driving LTC2185 ADC. In the application information of "Interfacing the LTC6403-1 to A/D ...
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0answers
78 views

Relationship between base resistor and collector current in this unbalanced differential amplifier

For this BJT circuit, I was wondering if there was a solution for how the collector currents change with respect to the value of the single base resistor. This arrangement popped up in a circuit I ...
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1answer
83 views

Comparator Undesired Behavior

The following circuit is a comparator, which compares input square signal at non-inverting pin with fixed reference voltage at inverting pin of integrated comparator circuit LM393 (\$R\$ is collector ...
2
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2answers
107 views

How to analysis this Operational-Amplifier circuit?

This is a reference buffer circuit that make a single-end audio input to be the differential inputs for ADC. Circuit-1: It does not like typical Op-Amp circuit of the same purpose like below. ...
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3answers
410 views

Understanding negative feedback in an inverting op-amp

Below is a basic inverting op amp. I'm having trouble seeing the negative feedback operation. simulate this circuit – Schematic created using CircuitLab If I understand the "golden rules" of ...
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1answer
176 views

Differential Amplifier to Scale Down DC Voltage

I'm using a 3.7V LiPo to power a device that normally runs on 3V (and draws about 100-200mA). I've determined that my device can run properly if I can achieve an output voltage that scales the input ...
1
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1answer
136 views

Common Mode and differential Mode gain of this Cmos diff Amp inverter

This is one of questions our prof gave to students in recent years and im preparing myself for this exam. What is Common Mode and differential Mode gain of this Cmos diff Amp inverter? i understand ...
4
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2answers
206 views

What step have I missed designing this differential amplifier?

First time posting on EE.SE and I hope this question isn't too broad. This will be a long post. I should also point out: I'm asking the process and not the solution the problem. I've did create a ...
1
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1answer
328 views

Output voltage of MOSFET differential pair with current mirror load

I've seen this circuit from https://www.allaboutcircuits.com/technical-articles/advantages-of-the-actively-loaded-mosfet-differential-pair/ How are the drain voltages equal?? I can't seem to figure ...
1
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1answer
561 views

Differentiator (Op amp) with a square wave

I'm working on a differentiator (op amp) with a unitary gain i calculated the value of RC and the period with a frequency of (1kHz). Figure 1. Differentiator Schematic (OrCAD). This is the schematic ...
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1answer
70 views

What is a good way to add a programable offset to a diffential signal?

I have an AC coupled, ~10 MHz to 1 GHz, differential signal, with a programmable gain, coming from a detector. The signal contain pulses, and the DC-balance is poor but constant (even if my hand ...
12
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5answers
2k views

Why are two stages used for an instrumentation amplifier?

When we have a two-stage instrumentation amplifier, such as the following. Why do we need the first stage of the two Operational Amplifiers? Couldn't we just input V1 and V2 into the differential ...
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0answers
55 views

Differential Amp - Bipolar transistor

I can't get the same answer as they are getting.. Here is what I'm getting: $$ Acc = \frac{V_{oc}}{v_{ic}} = \frac{-R\beta i_b}{v_{ic}} $$ $$ i_b = \frac{v_{ic}}{r_{\pi+2R_0}} $$ => $$ A_{cc} = \...
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1answer
505 views

Differential amplifier exercise problem

I am preparing for an exam and I am not sure if my solution is correct for this problem: We have a differential amplifier with 2 NPN transistors (T1, T2). T1's collector is directly connected to ...
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0answers
46 views

How can I bias this Differential amp. circuit at the best operating point?

I'm looking to find a way to bias this circuit: I've written down a couple of equations for DC load line(and also DC half circuit): and these two as AC Load line: Rc is given by 1K and you can see ...
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1answer
121 views

AC sources in DC analysis

Can I ground AC voltage sources when I do DC analysis of differential amplifier with BJT and current mirrors circuits?
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0answers
65 views

Is this gain calculated correctly?

In this schematic, if the T5 transistor is off and the T4 is on, what would be the incremental resistances ri3 , ro3. my guess is that: ri3 is : rPi4 + RE5 + Rspeaker. and ro3 is : RE5*(B+1) + ...
2
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1answer
262 views

Fully differential amplifier - adder?

I have two signal sources providing the same differential audio signal (VIN1 and VIN2). I want to sum those signals. The result (VOUT) shall also be differential. The idea is to take a fully-...
3
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4answers
488 views

Differential Amplifier's Unusual Behavior

This circuit is made of one differential BJT transistor pair and voltage-amplification stage with negative feedback. simulate this circuit – Schematic created using CircuitLab About this ...
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1answer
130 views

DC voltage in collector after active load

I am trying to analyse the DC Q bias point of the following circuits with a current source/mirror involved. I do not know how to calculate by hand the Q2 and Q5/Q4 collector voltages. All the currents ...
1
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1answer
261 views

Two diodes in input stage of power amplifier

Some of the power amplifier schematics include diodes in input stage like below. What is the purpose of them?
3
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3answers
439 views

A question about remote ground sensing and its advantages

In this article, they are explaining the benefit of using a technique called remote ground sensing by using a single-ended sensor and a differential amplifier or an instrumentation amplifier. Below is ...
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3answers
423 views

Distortion Elimination with Differential Transistor Pair

Most of you know that incorporation of negative feedback within amplifier is one of major considerations when designing a hi-fi amplifier. Till now, I have only dealt with differential transistor pair ...
10
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2answers
311 views

Another Failed Differential Amplifier

This is the circuit I made - designed it, calculated it, built it: simulate this circuit – Schematic created using CircuitLab Q1's and Q2's collector current was 5mA, while Q3's was 1mA. Sine ...
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4answers
646 views

How to apply 180 degrees out of phase signal at inputs of differential amplifier in laboratory when only one function generator is provided in lab?

In this differential operation experiment, two input AC signals have to be applied to the bases such that they are 180 degrees out of phase with each other, but I am not sure how to invert an AC ...
4
votes
1answer
479 views

Why modern oscilloscopes inputs are not fully differential (i.e. floating)?

This question is somewhat related to this other EE.SE question, and some hints are given there, but are not completely satisfactory for me. I've understood that, besides safety considerations, the ...
4
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3answers
2k views

Differential Amplifier Biasing Problems

This is the circuit that I built: (desired voltage levels are described next to the circuit) simulate this circuit – Schematic created using CircuitLab I tried to make proper bias conditions ...
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2answers
861 views

Differential Amplifier Transistor Pair

I have been dealing with these differential amplifiers for weeks now and still don't understand the basic principles of its operation and how should it be used inside an audio amplifier. I understand ...
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0answers
58 views

How to calculate the size for differential amp

In the baker's book (CMOS. Circuit Design, Layout, and Simulation) ,it just teach us how to calculate the gain,but it does't teach us how to calculate the size for a amp,take the differential amp for ...
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2answers
848 views

How to make amplifier (almost) Beta independent?

There are several ways to bias the quiescent point of transistor, when used as an amplifier. Among which voltage divider is best known for its improvements (improved temperature drift and beta ...
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1answer
213 views

Improved Differential Amplifier

I made this circuit as shown below: simulate this circuit – Schematic created using CircuitLab After those improvements with current mirror and constant current source were considered, this is ...
1
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1answer
162 views

Differential Amplifier Input Line-Level Signaling

This is the circuit I'm referring to: This stage is often used as input stage of audio amplifier. I am wondering, how can the input signal be normally amplified since there is no DC bias across the ...
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0answers
52 views

Differential transistor stage current not changing with temperature

I asked similar question recently, which also referred to differential transistor pair, but this one is different. I made this circuit (in real world): simulate this circuit – Schematic ...
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2answers
143 views

Differential Amplifier BJT Experimenting

This is a circuit I made recently; a differential bjt amplifier (without any signal, only DC). So I was trying to see, what happens when I change the voltage difference between the base of Q1 and ...
0
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1answer
113 views

Half of differential tage voltage gain

I can't understand why is 2Rpi in equation 375/376. It looks like the current ib1 goes through Rpi of first stage and through Rpi of second stage but it must go through first Rpi to ground and back to ...
2
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2answers
239 views

Differential Amplifier with Large Capacitive Load

I am experimenting with the following mixer circuit for audio: EDIT: SCHEMATIC FIXED All of the subcircuits work fine separately but when the diff amps are combined with the summer circuit, the ...
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3answers
234 views

Differential stage Av value with current sources

Why all books told that Av differential of an differential input stage in power amp is very big? Ad = Rc/re, but if there are current sources in the emitter and collector circuit they will have too ...
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1answer
263 views

How to find collector resistor value in bjt differential amplifier

What value R2 may have in that schema? Anyway it will be loaded by pn-junction of Q5 and will have fixed voltage drop near 0.65V. What value R2 must have if the current source is used instead R1? The ...