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Questions tagged [diff-amp]

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36 views

BJT current mirror with Early effect

I'm trying to determine the reference current for the BJT current sink to have a certain bias current value for the amplifier. I also need to consider the Early effect for the BJT. So basically I need ...
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0answers
58 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
68 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 ...
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0answers
31 views

Current source for discrete differential amplifier

I hope someone can point me to the right direction. Basically I face the same problem like the author of the following question. How do I choose the correct current for my differential amplifier? I ...
2
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2answers
78 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
78 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
77 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
79 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
181 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
238 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 ...
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1answer
240 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
61 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 ...
11
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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
54 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} = \...
1
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1answer
210 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
40 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
70 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) + ...
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0answers
35 views

Need help verifying this design that transmits light signal via op-amps and diff amps

I designed a system where a light signal is detected by a photo detector and transmitted over a PCB to a microprocessor. The photo detector had an internal resistance of 1KΩ and could at most generate ...
2
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1answer
172 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
394 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
96 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
186 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?
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3answers
294 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
349 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
260 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
460 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
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1answer
357 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
1k 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
619 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
53 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
600 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 ...
-1
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1answer
177 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
146 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
50 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
118 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
67 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
201 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
171 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 ...
0
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1answer
211 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 ...
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4answers
173 views

THS4521-HT: Op-Amp giving negative differential voltage

Can someone help to explain where I get wrong with this schematics? I use a differential op-amp THS4521 and want to measure the differential signal coming from a pressure sensor (transducer). The ...
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0answers
1k views

Differential amplifier input resistance

From this link the balanced gain and input impedance differential amplifier has such resistors: simulate this circuit – Schematic created using CircuitLab $$ R_1 = \dfrac{R_i}{R_i+R_f}R_i$$ $$ ...
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0answers
55 views

differential amplifier measuring current below supply rail

I am measuring the current from a battery (12v) using a shunt resistor. But if i can i want to use the normal rail as supply for the op-amp: Now my thinking is that because of the two voltage-...
0
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2answers
1k views

High Gain Amplifier using BJT

I need some assistance on building a high gain amplifier using only BJTs, capacitors and resistors. I have made some before using op amps, but for this assignment I am not allowed to use Op Amps at ...
1
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1answer
526 views

Single input impedance of long-tailed pair

I have following circuit: and I'd like to know input resistance of single input Ui. I tried to calculate it like this: if I increase Ui by little, there's some voltage drop on base-emitter junction (...
0
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2answers
71 views

Differential Op Amp Output voltage

I was just wondering if someone could tell me if I am doing this right, because I don't really have any sample problems but just want to be prepared for anything. If we wanted to find the output ...
0
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1answer
42 views

Differential Op Amp queston

So we are given the equation: Vout=Rf/Rs(V2-V1) I'm just wondering how would we solve it when the Rf/Rs are different values like they are in this circuit: simulate this circuit – Schematic ...
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0answers
574 views

Sallen-Key with fully-differential output — options?

I have a single-ended audio signal that I want to low-pass filter and convert to differential (with GND as the OCM voltage — that is, when one output is X Volts, the other output shall be −...
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2answers
658 views

Is high impedance important for a differential amp measuring a battery voltage?

I want to measure voltages of multiple cells which are connected in series. I want to do that using a differential amplifier. I read about low input impedance, and what to do about it in this case. So ...
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2answers
559 views

Increasing the Bandwidth of Differential Amplifier

I am working on the second stage of an operational amplifier which involve a BJT differential amplifier. I am trying to increase it's bandwidth (parts of the requirements) and was told by a TA that a ...