Questions tagged [differential-amplifier]

For questions about circuits that amplify the difference between two input signals but not the signal common to the two inputs (e.g. the long-tailed pair). Do not use for questions about operational amplifiers (which are a type of difference amplifier) unless the op amp is used as a differential amplifier -- use only the "operational-amplifier" tag for most questions about op amps (e.g. an op amp as an inverting amplifier).

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LM3900: different input impedances in symmetric pins?

Referring to the LM3900 "Quadruple Norton Operational Amplifiers" datasheet, consider the schematic of each single amplifier at page 1. simulate this circuit – Schematic created using ...
BowPark's user avatar
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1 answer
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How is the boundary of input CM level calculated?

I will briefly state my understanding of the following equation, and then pose three questions at the end. Equation (1) (2) refers to the circuit in the first picture, Equation (3)(4)(5) refers to the ...
Tong Su's user avatar
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1 vote
2 answers
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Designing a differential amplifier

I was trying to design a differential amplifier in which the collector resistances of the transistors are 2.2 kΩ and are biased at 1 mA and are supplied with Vcc= +/-5 V . To find the Ro (the ...
Anya's user avatar
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2 votes
2 answers
98 views

Why does shorting the drains linearize the transconductance of the differential amplifier?

Why, by shorting the drains in Fig \$14.15\$ in this manner, will it allow the \$G_m\$ plots to add together? What will happen to the \$G_m\$ plot if we swap the shorting transistors, i.e., shorting ...
Tong Su's user avatar
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3 votes
1 answer
70 views

How to break the feedback loop and add the loading?

I am trying to break the feedback loop of a fully differential amplifier and add the loading to the input and output: I want to do this to take into account the loading of the feedback network on the ...
mahmoud esmail's user avatar
2 votes
0 answers
98 views

What is the point of analysis and biasing calculations when real world performance is going to be much lower in analog circuits? [closed]

I am making a 3-stage audio amplifier as a course project. The first stage is a differential amplifier, the second stage is a common-emitter amplifier, following that there is a passive filter and ...
Koustubh Jain's user avatar
0 votes
1 answer
119 views

Op-amp question: Is this circuit possible?

I was (re)doing some electronic learning, and tried to come with a "general solution" for all op-amp circuits. I thought I could do so by having an op-amp with both negative and positive ...
LittlePanic404's user avatar
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3 answers
95 views

What is the difference amplifier common mode voltage?

In some sources it is stated that v1 is directly equal to Vcommon mode voltage in difference amplifier, but isn't Common mode voltage (V1)/2 as calculated?
Electronx's user avatar
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4 votes
2 answers
476 views

Why won't this differential amplifier work without these two additional resistors?

I'm trying to measure a differential voltage in LTSpice using the following structure: The simulation results are correct, the voltage at the output is very similar to the differential input voltage. ...
FernandoPT's user avatar
1 vote
0 answers
116 views

Having trouble simulating a two-stage differential amplifier in LTspice

The following is an LTspice simulation for a two-stage differential amplifier. The simulation takes hours. What am I doing wrong? Spice netlist: ...
kile's user avatar
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Does a single input differential amplifier remove noise?

It is known that the purpose of using a differential amplifier is to remove noise from the input signal, apart from giving some small amplification. To my knowledge, there are two inputs and two ...
Soumil Gupta's user avatar
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1 answer
92 views

How to improve gain in this amplifier?

I want to design an amplifier to drive an 8 ohm speaker. I am using a differential amp as the first stage, and then a class AB amplifier (inspired by the one I found here class AB amplifier distortion)...
Koustubh Jain's user avatar
0 votes
1 answer
119 views

Differential amplifier op-amp schematic connection and DC biasing

I have a differential IF (intermediate frequency) signal generated by an ADL5801 RF mixer. Stage 1: the signal is amplified before active filtering and it has LC LPF in the beginning for filtering ...
Cenk's user avatar
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1 answer
138 views

Op-amp schematic connection questions and DC biasing

In the first stage the signal is converted to single-ended, and it is amplified using a digital potentiometer in the second stage to be able to change the gain with a microcontroller. In the last ...
Cenk's user avatar
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1 vote
2 answers
210 views

I would like to know what type of op-amp this circuit is

This circuit is connected to 250V AC power and I would like to calculate the values ​​of the resistor and capacitor, but I don't know which formula to use to calculate it. I think this circuit is ...
Noting's user avatar
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1 answer
102 views

Single Ended to Differential Conversion with Opamp and Correct DC Biasing Method

First schematic below is the initial gain stage of the intermediate signal generated by mixer of radar. It is passed through sallen key high pass filter. Second schematic for differential to single ...
Cenk's user avatar
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0 answers
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Voltage gain of differential amp with active load (OTA)

In solving the differential pair with an active load and parasite resistance R1 is included, I am stuck on how to proceed. This was a question from Razavi's Design of analog CMOS integrated circuit, ...
Gol's user avatar
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3 answers
104 views

How can I step down 134V efficiently for the high side voltage supply for an AMC1200BDWVR?

I am using a fully-differential isolation amplifier. I want to make the high side regulated voltage of 5 V with as few components as possible, so I have built a “resistor-diode” regulator as shown in ...
ManeGote's user avatar
1 vote
1 answer
68 views

Balance Mic and Speaker for Camera Input with Ground Loop Isolation

Novice looking for some help. I use a Cardo Bluetooth headset to communicate with friends and record the audio onto an action camera while out riding motorcycles. By trial and error I was able to come ...
simi.d's user avatar
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2 votes
1 answer
82 views

Differential Signal Amplification with Op-Amp DC Biasing Problem

The example circuit on the schematic generates square wave like output and the signal appears at the top of that square wave (see the scope output screenshot). All i need is to amplify differential ...
Cenk's user avatar
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1 answer
76 views

Ways to output "negative" components of a sine wave through an op-amp

I have two sine waves of 1V magnitude and offset of 2.5V with 180 phase difference, going into a differential amplifier to be amplified. I have access to a 5V source (as a source, not as a battery) ...
HFOrangefish's user avatar
3 votes
1 answer
221 views

Failed to simulate active current mirror in LTspice

The following is my schematic for active current mirror: This is a SPICE simulation for my old question: The following is the \$V_{out}\$ plot. What's wrong with my \$V_{out}\$? The asc file is ...
kile's user avatar
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0 votes
3 answers
145 views

Instrumentation Amplifier improper frequency response

Followup to this question. I have an instrumentation amplifier. When conducting an AC Sweep, this is the response. There are two issues with this. Firstly, the signal magnitude is far too low. ...
HFOrangefish's user avatar
0 votes
1 answer
182 views

Should gain of this differential circuit be absolute value?

Content is from the book Design of Analog CMOS Integrated Circuits (https://electrovolt.ir/wp-content/uploads/2014/08/Design-of-Analog-CMOS-Integrated-Circuit-2nd-Edition-ElectroVolt.ir_.pdf) on Page ...
kile's user avatar
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1 vote
3 answers
125 views

Transfer function of an op-amp circuit with inverting feedback and dual input

Given the below circuit containing two ideal op-amps, how can I find the transfer function? I am confused by the \$-K\$ op-amp. Typically we need to find a transfer function like $$V_0 = f(v_1,v_2)$$
jimmy_p's user avatar
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1 vote
1 answer
74 views

Differential input impedance derivation

I have been looking into differential amplifier circuits, differential input impedance, and common-mode input impedance. Everywhere I go (such as here or here), I see this as the solution for ...
HFOrangefish's user avatar
0 votes
2 answers
100 views

Differential amplifier gain calculation

I am currently working on a project and I found this differential amplifier for a shunt. I perfectly understand what is going on with the voltage follower op-amp, but I dont understand what is going ...
Pablo9026's user avatar
0 votes
2 answers
99 views

Differential amplifier not gaining

I have designed a differential amplifier circuit in NI MultiSim using the LTC2050, with an expected gain of 15, connected to a strain gauge in a full bridge configuration. However, the gain I am ...
HFOrangefish's user avatar
0 votes
1 answer
106 views

Transfer Function of Differential opamp with common mode voltage

When we consider the relationship between Vout and Vin of the differential amplifier, we connect one of its inputs each time to the ground to ignore that input voltage in the calculation, in order to ...
TSLee's user avatar
  • 157
4 votes
2 answers
241 views

Summing Op-Amps vs Difference Op-Amps

How do you tell the difference between a summing amplifier (non-inverting) op-amp and a difference amplifier just by looking at its configuration? Please note that in both of these cases, both the (+) ...
HDY's user avatar
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2 votes
3 answers
148 views

How do you turn on an LED when the input voltage is less than 12V?

I am designing a device that will check whether a fuse box motherboard is outputting 12V or not. I first considered diodes as they each have a 2V drop so I had 6 in series and functioned well but ...
chambers02's user avatar
1 vote
1 answer
102 views

Closed-loop differential-input JFET amplifier

I am unsure how a differential-input JFET amplifier in a closed-loop can be built. A very simple amplifier with differential inputs and differential outputs can look like this: As far as I understand,...
Charly's user avatar
  • 702
0 votes
1 answer
39 views

Why does the offset voltage have this polarity?

Consider the following from Chapter 3.5.6 of Analysis and Design of Analog Integrated Circuits by Gray, Hurst, Meyer, and Lewis: As I ask about in a separate question, the authors claim that for some ...
EE18's user avatar
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2 votes
6 answers
244 views

Why is an offset voltage and an offset current sufficient to represent mismatches in a differential amplifier?

Chapter 3.5.6 of Analysis and Design of Analog Integrated Circuits by Gray, Hurst, Meyer, and Lewis (GHLM) discusses the effect of device mismatches on the behavior of emitter- or source-coupled ...
EE18's user avatar
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0 votes
0 answers
43 views

Differential Amplifier with the same entrance in both inputs

So, I'm supposed to find an equation that relates the output and input of an OpAmp. For both zero and first order. The circuit is the one in the image, it should be easy, since it's a Differential ...
Brisingr's user avatar
0 votes
1 answer
101 views

Single source, single-ended to differential output low pass filter

I want to design an IEPE sensor signal conditioner. This signal conditioner that I will design will not include gain and attenuator parts. The signal from the IEPE sensor will pass through the ...
Electronx's user avatar
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1 vote
1 answer
28 views

Are Differential Line Drivers same as FDA or similair as Balun ? How we use them differently?

I'm trying to understand the difference between differential line drivers, FDA and baluns. I know that FDA and Blaun both can be used to driver ADCs and baluns are usually AC coupled and adding less ...
X.LI's user avatar
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0 votes
1 answer
105 views

Understanding this MM/MC discrete phono stage

I am challenging myself at understanding my integrated amp's MM/MC phono stage; The amp is a Rega Elicit mk. I. It is a somewhat complex design and as a hobbyist I'm out of my league. The circuit ...
Joe's user avatar
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2 votes
0 answers
58 views

Transmitting differential video signal to the ADC input

I'm designing a circuit that converts a single-ended analog video signal (f = 10 MHz) to a differential pair and then is processing the data to a digital form. The signal is transmitted through a ...
drydre's user avatar
  • 75
0 votes
2 answers
58 views

Wheatstone bridge to voltage follower circuit not working as expected

I am designing the following circuit shown in the atached image. It is a wheatsone bridge with the differential output attached to voltage followers on each terminal and then connected to a single ...
ecp's user avatar
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1 vote
2 answers
214 views

Would this be an acceptable implementation of an OTA-based voltage regulator?

I am building a discrete voltage regulator, centered on a differential pair with an active load. I have seen the single stage differential pair being called an Operational Transconductance Amplifier. ...
Virgil_Tibbs's user avatar
2 votes
1 answer
75 views

Designing a single-ended to differential driver to DC2588A-A evaluation board

I'd like to test the DC2588A-A, and I noticed that the user guide mentions it's driven by a pair of ADA4899-1 DRIVER amplifiers. However, the user guide doesn't provide clear information about the ...
Abdel Djaferbey's user avatar
0 votes
3 answers
115 views

Op-Amp circuit that works as integrator and differentiator

Determine the conditions for the circuit to act as a differentiator and integrator. Determine Avlc for both situations. C = 100nF R = 1k ohm The closed loop gain for this circuit is: $$ A_{vLC} = \...
Felipe Gorcóa's user avatar
0 votes
3 answers
139 views

What type(s) of analysis should be performed on a discrete voltage regulator circuit?

I am tasked with building a fully discrete voltage regulator. I am restricted to only using discrete components, such as transistors, diodes, resistors etc., no ICs are allowed. Something like this: ...
Virgil_Tibbs's user avatar
1 vote
2 answers
154 views

Input common mode voltage in differential amplifier used for high-side current sensing

I am confused about the input common mode voltage seen by an op amp configured as a differential amplifier for high side current sensing. Assuming that the op-amp and the load for sensing share the ...
Jackson's user avatar
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0 votes
2 answers
104 views

Minimizing noise with single-ended opamps

Opamps often get used with one input at a DC voltage, usually the main ground per the standard inverting amplifier example: For low noise, a BJT input stage like OPA1611's is often chosen for the ...
bobuhito's user avatar
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0 votes
0 answers
93 views

Differential Amplifier with unbalanced differential signal

The circuit topology of figure 1a corresponds to a differential amplifier with resistor load. Since the signal generator available in lab does not have a differential output, a balanced differential ...
Aleat's user avatar
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0 answers
72 views

How to calculate the time constant of a simple cross coupled diff pair latch circuit

I have a circuit, which is given below. Now I want to find the time constant of the circuit, considering there are equal caps placed at node X and Y. For a small signal model I can easily find the ...
thehappywine's user avatar
3 votes
1 answer
108 views

Amplifier circuit design for ADC: Could input voltage mix with reference voltage?

This might be a silly question. I saw this from "Opamp For Everyone" and was a bit confused with this circuit. The book doesn't mention the signal source at all, I think it does have a ...
TSLee's user avatar
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1 vote
0 answers
101 views

Is this a valid way to determine which diodes are on in an op-amp based rectifier?

Consider the circuit above, where we are treating the diodes as ideal. Let's take the case where Vs < 0. Since V- = V+ = 0 for both U8 and U9, that automatically means the current is to the left ...
Adam Herbst's user avatar

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