Questions tagged [rail-to-rail]

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Rail to rail +12/-12 V square wave generation with microcontroller

I need to generate a +/-12 V square wave, +/-0.4 V tolerance is allowed. The purpose is to drive the pilot signal of an electric vehicle level 2 charger, for those curious. EDIT (clarification): what ...
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  • 301
1 vote
1 answer
73 views

Understanding Summation of Currents in a Rail to Rail Differential Stage

In order to understand rail to rail OpAmps I consulted a (german) textbook. There, I found this principle schematics: So far I understood, there are two complementary differential input stages (T1, ...
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  • 257
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0 answers
39 views

Tradeoff between (op) amplifier voltage range and offset and settling

I know that an amplifier (let's take an op-amp) can't swing rail-to-rail. The reason has to do with the load device. For example, in a normal common gate/common base amplifier, the load device causes ...
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4 votes
3 answers
523 views

Unused Opamp Termination: How does it cause increased current consumption?

Usually the following configuration for unused opamps is said to be troublesome, even for rail-to-rail input & output (RRIO) opamps. Nevertheless, it is attractive because it requires no ...
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46 views

Does a rail-to-rail input fully-differential amplifier need Common mode feedback at Output nodes?

I am designing an Op-amp with rail-to-rail inputs and the operation being fully differential in nature. I am trying to understand whether I will still need a CMFB (common-mode feedback) circuit to fix ...
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1 vote
1 answer
220 views

OpAmp/Comparator for AC current detector circuit

I am trying to complete schematic for current detector. This is addition on How to build AC current sensor circuit for ESP-01 GPIO. By googling and researching I came with following schematic which I ...
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  • 87
1 vote
1 answer
264 views

TL072 opamp clipping problem

I'm trying to drive a TPA6120 headphone amplifier with TL072. I use single 24VDC supply with a TLE2426 virtual ground. The TL072 works well and puts out around 21Vp-p sine wave. But as soon as I ...
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  • 55
3 votes
2 answers
329 views

Why is my op amp railing?

So I have a LM358 Dual opamp. I only care about the first op amp, the second I just have set to put out 12V to keep it from floating. The the first is reading in feedback from a 1k potentiometer from ...
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1 vote
1 answer
502 views

Simulating PMOS differential amplifier in Cadence

I am studying about rail-to-rail opamp design and I am trying to recreate the Itail vs Vgs (in this case input common voltage) curve from the link bellow (pages 5 and 6): https://mixsignal.files....
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  • 53
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202 views

Push pull output stage max output voltage

Spent a day trying to understand the maximum and minimum output voltage of the basic circuits as shown in this figure The problem is that I have come across different expressions for the output ...
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  • 169
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1 answer
85 views

Is it possible to replace the ref pin of AD620A with a fixed voltage?

I am trying to implement the below circuit (from) without ADuC842, I will use Arduino mega2560 ADC. the circuit generates -5V to 5V rail to rail voltages for ad620a and they control ref voltage via ...
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  • 322
0 votes
4 answers
463 views

Is exceeding Opamp Common Mode Voltage safe?

I understand that when you exceed an Opamps Common mode voltage limit that the output will no longer be reliable. And that this limit is often a bit less that the supply rails. But would slightly ...
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  • 487
0 votes
3 answers
171 views

How can I check in an OpAmp datasheet if the OpAmp is push-pull?

I am looking for an OpAmp which I want to use as voltage follower after a DAC. The OpAmp should be able to pull 3mA. And it should have Rail to Rail input and output. How can I check in a datasheet ...
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  • 203
4 votes
2 answers
663 views

How does a common-emitter rail-to-rail opamp output stage work? Is there a discrete example?

I'm reading an article about how a rail-to-rail opamp works. The materials from Maxim and Analog Device all mentioned that, in a conventional operational amplifier, the output stage, in its essence, ...
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  • 3,857
0 votes
1 answer
323 views

Is it a Rail-To-Rail opamp?

I ordered several LMC6482IN opamp without reading the datasheet details! I want to measure high side current with mA accuracy, for that I need the opamp output to go all the way to ground 0V. in the ...
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  • 1,974
2 votes
2 answers
165 views

High voltage op amp rail generation

I'm using two ADHV4702-1 high voltage op amps for a project. They are configured as a current sink with a class B output amplifier (with some fixes for the crossover distortion). I already have a +/-...
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  • 180
2 votes
1 answer
996 views

What is the difference between differential rail-to-rail, push-pull rail-to-rail and rail-to-rail OPAMPs

I'm loking for an rail-to-rail OPAMP to my project. I need a OPAMP that fed by a 12V and a -5V power supplies can generate an output voltage near these values, at least, near the positive 12V, the ...
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  • 835
1 vote
3 answers
941 views

How can I determine whether this is a "rail to rail" opamp from its datasheet?

I know that rail to rail means that the opamp output can have a swing upto its power rail voltages. So for a rail to rail opamp lets say if the supply test condition is +-12V, I would assume that the ...
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  • 1,514
2 votes
4 answers
3k views

Are there any single supply OP amps with negative supply voltage?

I learned that basically the only difference between a "single supply" OP amp and a dual supply one is that the former can drive much closer to the negative supply rail. Furthermore if I understand ...
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0 votes
1 answer
131 views

Loud hum and buzz... I think I know why but I don't know how to solve

First, read this other question of mine. I have modified the amplifier, as suggested by τεκ to run on the full rail. This is the modified circuit. Notice how the amplifier ground is tied to -5 and ...
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  • 767
0 votes
2 answers
84 views

Truncating negative results of Op amp by rail limiting

I have a signal that will swing from -5v to 5v. I am interested in the 0 to 5v part only. I will set a reference voltage and give it and the signal into a comparator. The comparator's rails are 0, and ...
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  • 233
1 vote
2 answers
7k views

No amplification with LMV358 compared to LM358 in crude current sensing

I am trying to build a current sensing circuit (two channels), with no requirement of precision (i.e., is current passing over some threshold whatnot). The (somewhat generic) circuit I am implementing ...
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  • 13
2 votes
1 answer
114 views

Comparator circuit undesirable fluctuations

I have designed a comparator with hysteresis and rail to rail operation and my output depicted in figure1.The inputs of the comparator is a sine wave signal and a triangular waveform as shown below....
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  • 121
4 votes
3 answers
2k views

How do I see if an op-amp is rail to rail using only datasheet?

If I have a data sheet or part of it, how can I see if an op-amp is rail-to-rail using only the numbers? For example, only using the image below, how can I see if input and/or output is rail-to-rail?
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2 votes
1 answer
109 views

Rail to rail amplifier analysis problem

Can someone help me to understand what we expected in the output(Voutn,Voutp) of the circuit of figure 1?I have searched for months a lot of books but I can't understand the operation of the rail to ...
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  • 121
1 vote
3 answers
2k views

1-5V to 4-20mA voltage drop problem

I'm hoping someone can help me remedy this problem (or at least come up with a temporary solution), as I am a novice in electronic circuits. The below circuit shows my setup. Vin is my input signal ...
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1 vote
2 answers
298 views

LMC6062 Jumps too Rail when 1V below

simulate this circuit – Schematic created using CircuitLab I'm using a precision OP AMP LMC6062AIM as a buffer (Voltage follower). The supply is +5V and GND. The INPUT is a DC voltage (no ...
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10 votes
2 answers
25k views

What does "rail to rail output opamp" mean?

Context: I have a very similar problem to the one exposed here, and in the best rated answer (by Olin Lathrop), he says we need a rail to rail output opamp. My question: What is a rail to rail opamp? ...
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0 votes
1 answer
92 views

How to understand rail to rail input circuit?

I watched an input circuit for ground rail as follows, Why do I have to place a current source here? If I place a resistor instead, there will still be current flowing in emitter-base direction for ...
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  • 855
2 votes
2 answers
477 views

What OP AMP spec should I be checking to assure this behavior

Recently, on the advice of others on another thread, I tried to migrate a dual supply OP amp circuit to single supply version. I needed a quad OP AMP, and the logic was that since my final circuit ...
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