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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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Confusion with two types of differential signal coupling

I'm having difficulty to articulate the question. But perhaps I might get close to it by an example. I know that in differential signaling, both the signal and the receiving amplifier can be in ...
user1245's user avatar
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0 votes
0 answers
30 views

MOS differential amplifier output swing

Why is the maximum output voltage swing of a MOS differential amplifier 2Vdd-4Vdsat? I understand that the voltage swing of a MOS CS amplifier, but I don't know how they got that the voltage swing of ...
bungfortnite123's user avatar
1 vote
0 answers
54 views

Working of differential pair using MOSFETs

I am currently learning about differential pair using MOSFET from this course. In this particular lecture, the teacher says that to have a differential pair we need to apply the second signal v2 at ...
tinkerer's user avatar
  • 180
1 vote
1 answer
41 views

Common-mode choke in ECG circuit

I'm designing a PCB for single lead ECG measurement and I ran across this TI reference design that contains a common-mode choke (P/N Murata DLW31SN900SQ2L). What's strange is that I can't find any ...
Adam Jones's user avatar
0 votes
0 answers
16 views

AD8232/AD8233 not working for sEMG

I am working on an sEMG circuit using the AD8232 and cannot figure out what is going wrong, the circuit isn't outputting the correct signal when connected to the forearm. I am using the 3 lead ...
user2608683's user avatar
1 vote
0 answers
54 views

Is it safe to flip the use of resistor pins of the INA106 differential amplifier to turns its gain from 10 into 0.1?

I'd like to have differential amplifier with gain of 0.1 without having to put any external resistor. Most of them in the datasheet states the use of gain of 1 or more and rarely specify the use of ...
Unknown123's user avatar
0 votes
2 answers
96 views

Differential amplifier Q point

I'm looking for a way to solve the Q point of this amplifier I found this set of equation : EQ1: I=Ic3(1+1/Beta3)+Ic4(1+1/Beta4) EQ2: Ic1/Beta1+Ic2/Beta2=Ic4-Ic2 EQ3: Iout=Ic3-Ic1 EQ4: Ic1(1+1/Beta1)*...
exolune's user avatar
  • 59
1 vote
4 answers
72 views

Can differential probes be used with floating oscilloscopes, such as handheld/tablet scopes?

I am in the market for a differential probe (and possibly a handheld oscilloscope down the track for field work). One seller I came across has a warning for many of the probes that they sell saying &...
daviegravee's user avatar
0 votes
1 answer
77 views

Distortion in a negative channel of the differential amplifier THS4505

I designed a single-ended to differential signal amplifier using a tool provided by Texas Instruments: The source signal passes through a voltage follower (OPA810IDBVR), so the output resistance ...
drydre's user avatar
  • 75
0 votes
0 answers
54 views

differential gain for mismatched \$g_m\$ in differential amplifiers

I couldn't understand how the author came up with the expression of differential mode gain. He states to look from the Fig 4.17 to derive this expression, whereas the fig 4.17 has no mention of \$R_{...
wolff's user avatar
  • 13
0 votes
0 answers
89 views

Gain bandwidth calculation of two stage op-amp

I want to design a two stage single ended OTA without using a Miller compensation capacitance. Every source that I have examined gives a design example with a compensation capacitance. Hence, they ...
Aldrich Taylor's user avatar
1 vote
1 answer
104 views

Differential Amplifier Output Ringing

I designed this circuit. It is a fully differential amplifier of gain one. I am getting this ringing and noise on the output of tx1_o Blue is where the probe is and ground is on circuit's ground. Here ...
Ishmael's user avatar
  • 11
0 votes
2 answers
68 views

How can i obtain a positive Vref for this circuit?

I have to design a irrigation system that uses a resistive moisture sensor to maintain a certain level of relative soil humidity for a plant. In order to convert the resistance changes of the moisture ...
m3ll0w's user avatar
  • 41
0 votes
0 answers
69 views

Differential input resistance of non-symmetric circuits

In Sedra and Smith (7th edition, section 2.4.1) when building up to an instrumentation amplifier there is discussion of how to use a single op-amp (differential input, single-ended output) to ...
Halleff's user avatar
  • 675
2 votes
1 answer
389 views

Why does my common mode test still have tiny retained sine wave?

I used this equipment the BMA-200 with the AMP01 having a CMRR of 125dB. I connected the signal generator output to both the In+ and In-. Yet the waveform still have retained sine wave of very small ...
Jtl's user avatar
  • 847
0 votes
0 answers
41 views

Noises when unused inputs not shorted with common V-

Update. Manufacturer confirmed all the 4 red V+ inputs used same blue V- and ground. Now what would be the noises introduced if only channel 1 is used and the 3 other inputs are floating (all ...
Jtl's user avatar
  • 847
0 votes
2 answers
63 views

PCB trace impedances of integrated circuits with high input impedance

There is an ADC front end IC (opamp) at the input of my ADC card and it has high input impedance, What should I set the differential trace impedance to when drawing the PCB? Does this matter much?
Electronx's user avatar
  • 756
2 votes
1 answer
161 views

Unknown 958Hz peak in amplifier/ADC with any input (shorted, opened, signal generator, real signal) [closed]

Update 2: I disconnected the ground between channel 1-4 from channel 5-16 and the 958Hz peak disappears. It could be crosstalk but i wonder why crosstalk can produce 958Hz noise. Update: Using the g....
Jtl's user avatar
  • 847
5 votes
4 answers
476 views

Ground in differential opamp situation

I have a setup like such in the provided schematic. The idea is that I do have a -2.5 to 2.5V signal which I'd like to convert to a signal between 0 and 5V. How should I connect my opamp? Should the ...
Mart's user avatar
  • 376
3 votes
2 answers
429 views

How to share a single gain resistor among multiple op-amps in a circuit

I'm currently designing a circuit where I need to implement multiple op-amps, each configured with the same variable gain resistor using a single digital potentiometer. To simplify the design and ...
Bored's user avatar
  • 33
0 votes
1 answer
42 views

Negative Voltage at Transistor bases in my Differential Amplifier

I am supposed to calculate the differential input resistance but the voltage at the base of the transistor is negative so according to my formula I will have a negative resistance which is most likely ...
Cezar Cristian Gheorghe's user avatar
0 votes
1 answer
120 views

Noises are measured over a bandwidth. Is 50Hz and 900Hz noise the same at 1kHz bandwidth? [closed]

They say noise is over a bandwidth. At a bandwidth of 1000Hz. Is the noise at 50Hz and 900Hz similar? If yes. Please made a quick drawing how the noise at 50Hz and 900Hz look like roughly so I can ...
Jtl's user avatar
  • 847
0 votes
2 answers
104 views

How to measure fully differential amplifier input impedance in PSpice?

Before the differential ADC, I have a fully differential amplifier as the front end. I want to simulate and measure differential input impedance. My working range is max. 20 kHz. Why am I using the ...
Electronx's user avatar
  • 756
4 votes
3 answers
152 views

How does the current and voltage stabilize in a differential amplifier?

I am trying to learn how differential amplifiers work, and I would like to be able to visualize how the voltages and currents stabilize if the input voltages are changed. Specifically, I'm caught up ...
shafe's user avatar
  • 363
3 votes
1 answer
65 views

3x analog signal multiplier

I was looking for sin(x) in, sin(3x) out. I am aware of PLL, diode, and AD632 multipliers. Most are either squarers for sin(2x) or pure sine or amplitude multipliers. I saw the sin(a+b) identity and ...
George Dryden's user avatar
0 votes
2 answers
62 views

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
  • 748
1 vote
1 answer
125 views

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
  • 113
1 vote
2 answers
215 views

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
  • 43
2 votes
2 answers
101 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
  • 113
3 votes
1 answer
100 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
103 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
121 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
0 votes
3 answers
153 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
  • 756
4 votes
2 answers
488 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
121 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
  • 907
0 votes
1 answer
146 views

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
0 votes
1 answer
96 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
134 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
  • 75
0 votes
1 answer
141 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
  • 75
1 vote
2 answers
252 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
  • 57
1 vote
1 answer
113 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
  • 75
1 vote
0 answers
96 views

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
  • 11
0 votes
3 answers
109 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
108 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
  • 13
2 votes
1 answer
85 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
  • 75
0 votes
1 answer
98 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
244 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
  • 907
0 votes
3 answers
200 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
206 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
  • 907
1 vote
3 answers
136 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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