# Questions tagged [diff-amp]

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120 views

### Can we explain the differential pair in terms of resistances?

It has always been a big challenge for me to find the most general ideas behind great circuit solutions that can be illustrated by simple electrical concepts... and even by non-electrical analogies ...
110 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 ...
49 views

### Differential gain of op amp

So I was reading the chapter on Op Amps in Microelectronic circuits by Sedra, Smith, the topic on Differential Amplifiers to be exact. Here's the amplifier: https://i.stack.imgur.com/3qWzi.png To get ...
87 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?
29 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 ...
45 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 ...
143 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 ...
42 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 ...
99 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 ...
40 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 ...
66 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 ...
100 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 ...
36 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'...
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 ...
61 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 ...
67 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 ...
85 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 ...
86 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 ...
112 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. ...
472 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 ...
189 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 ...
141 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 ...
209 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 ...
337 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 ...
585 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 ...
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 ...
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 ...
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} = \...
543 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 ...
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 ...
129 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?
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) + ...
270 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-...
492 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 ...
135 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 ...
268 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?
457 views

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 ...
437 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 ...
318 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 ...
669 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 ...
493 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 ...
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 ...
889 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 ...
61 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 ...
874 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 ...
216 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 ...
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 ...
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 ...