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Questions tagged [diff-amp]

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1
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1answer
54 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
149 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
134 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
145 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 ...
0
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1answer
56 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 ...
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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} = \...
0
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1answer
81 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
37 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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0answers
43 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
34 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 ...
1
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1answer
135 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
336 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 ...
0
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1answer
76 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
152 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
240 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
297 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
237 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
345 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 ...
3
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1answer
265 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
976 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 ...
0
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2answers
494 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
454 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
148 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
122 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
45 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 ...
0
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2answers
102 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
52 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
votes
2answers
167 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 ...
0
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3answers
147 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
votes
1answer
178 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 ...
0
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4answers
149 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
725 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
53 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
434 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
66 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
39 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 ...
1
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0answers
472 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 −...
0
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2answers
478 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 ...
0
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2answers
463 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 ...
0
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1answer
194 views

Minimum CMRR design requirement

I've just started studying op amps recently and I am having trouble with the following problem from my textbook: Design the difference amplifier circuit to realize a differential gain of 1000, a ...
1
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1answer
2k views

Differential-output op-amp vs. additional inverting op-amp?

I'm wondering what the real advantages of op-amps with differential outputs are (e.g., AD8138), compared to just taking a signal V+ and feeding it to a unity-gain inverting amplifier to obtain a ...
1
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2answers
354 views

NPN Differential Pair - Emitter Voltage Variation

My understanding of how this circuit should work is : DC: The transistor bases are at about 0V DC due to R5 and R6. Some base current flows due to the constant current bias, so there is a small (~...
1
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1answer
311 views

Transfer function of a LM380 power amp

This is an exam question. Our professor has some generator of tests and out of the blue this beast came. We couldn't ask for the clarification, being an exam question, but from what I can see it ...
0
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2answers
92 views

Instrumentation or Differential amplifiers for milliohm measurement circuit design

I have got a design for milliohm measurement circuit that I have found on YouTube. Also avaliable in pdf format. This design uses the INA106U diff amplifiers and I want to replace it with ...
2
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2answers
1k views

Op Amp CMRR problem

I'm studying on my own for an exam. I bumped into this problem that really got me. My answer just doesn't match. Find the CMRR of the operational amplifier above, consider Ad = 1000000 (Answer CMRR= ...
2
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2answers
325 views

Why are these instrumentation amplifier circuits equivalent?

I am confused about the circuit of an instrumentation amplifier. In class we solved the following example: simulate this circuit – Schematic created using CircuitLab No big deal; with negative ...