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Opamp
Sci.Electronics.Basics is a worldwide Usenet news group that is used to discuss basic electronics questions.
We found 267 threads matching "opamp"
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The most relevant threads are listed first
Load seen by opamp
2008-10-25 05:33:00
Hi,
1)If i use an opamp with resistor feedback (for example in inverting
configuration with gain -R2/R1), the output resistence seen by opamp
is one resistor of R2 value?
2)for an opamp used in noninverting configuration (with gain 1+R2/R1),
the output resistance seen by opamp is R1+R2?
Thanks...
Single supply opamp calculations
MRW - 2007-06-18 15:02:00
Hi, I'm doing some more opamp calculations just to get used to opamp
golden rules some more. I decided to do an ideal analysis on an
inverting, single-supply opamp: http://i14.tinypic.com/5xebi4w.jpg
After applying some golden rules, I got the following equations:
(V1 / R1) + (Vo / R2) - [ (...Re: Special op amp "tricks"
John Fields - 2007-05-10 19:27:00
On Thu, 10 May 2007 16:20:05 -0500, "Jon Slaughter"
wrote:
> Are there any tricks I need to be aware of for practical op amp circuits?
> Mainly stuff to do with audio?
---
Yes.
1. Consider the opamp inputs holy and _ALWAYS_ have the ends of the
resistors connected to the opamp in...Opamp preamplifier design question
MRW - 2007-05-31 15:14:00
I'm working with these microphones because I have them already:
http://www.knowlesacoustics.com/knowlesacoustics-apps/microphone_productdetail.do?product_id=12
Assuming that the voltage output of the mic at 40dB re 20 uPa is 5
microvolts, would using two opamp stages for a pre-amplifier circuit...Re: Linearily of Derivative Circuits At High Frequency
John Larkin - 2010-08-07 12:12:00
On Thu, 5 Aug 2010 16:39:25 -0700 (PDT), Bret Cahill
wrote:
> To get to a higher frequency, is it possible to just use a smaller cap
> and/or resistor on op amp derivative taking circuits?
What do you mean by "get to a higher frequency"? Do you mean "continue
to be accurate at a higher...Choosing voltage opamp
Vitaliy - 2006-09-23 13:05:00
Hello,
I'm looking to add the 2nd stage to photodiode transimpedance
amplifier. All I want to achieve by 2nd stage is voltage gain and
capability to drive 50 Ohm loads. The first stage is OPA657.
1) a) Given power supply for opamp +-5V, should I select the opamp that
has Io,max=> 200mA. I d...confused about opamp circuit from practical electronics for inventors
panfilero - 2007-07-27 00:38:00
hello, OK, I've been breaking my head over this one for a while and
just can't figure it out. It's an example from a book called
"Practical Electronics For Inventors" It's basically a "Simple
Triangle-wave/Square-wave Generator" It has a integrator opamp
circuit feeding the non-inverting inpu...Conceptual design of a constant volume control opamp circuit
MRW - 2007-01-30 16:24:00
Good day:
I don't know how to word these properly. I'm really confused right
now. I'll try. If I were to design a single supply constant volume
control opamp circuit, would it be right to assume the following:
- In coming up with a conceptual block diagram, I take a sample of the
input s...OpAmp differential voltage range ?
Hammy - 2008-10-14 13:58:00
I thought I found an ideal micro power OpAmp for another low power LDO
I'm building in the LMV641. Small offset, RR output, 10MHz GBW, 2.6
V/us and still pretty good drive capability +/- 20mA.
http://www.national.com/ds/LM/LMV641.pdf
There's one thing I'm concerned about it specs a max diffe...Re: Does anyone know a way to take an audio signal and output it multiple times with different amplitude and phases tia sal2
John Fields - 2008-11-12 14:53:00
On Wed, 12 Nov 2008 19:04:07 GMT, please_post_to_groups
wrote:
> Does anyone know a way to take an audio signal and output it multiple times
> with different amplitude and phases tia sal2
>
> Greetings All
>
> I have one source for an audio signal and would like to send it to 8 differ...Calculating Input Noise Voltage
MRW - 2007-05-31 13:07:00
I was just checking out various opamp datasheets. I encountered this
opamp:
http://focus.ti.com/lit/ds/symlink/tlv2784.pdf
In the few lines of text, it says that the input noise voltage is 9 nV/
sqrt(Hz) at 10kHz. But in the table at the bottom of the page, it says
that the input noise voltag...neg ldo problems
Hammy - 2010-02-25 08:49:00
I'm guessing I'm missing the obvious here. I'm trying to build a
discrete negative LDO using a NFET for the pass element. I'm basing it
on the internal structure of the UCC284-5 seen here.
http://i50.tinypic.com/orkroj.png
I've tried inverting the output of the opamp with a BJT but its n...Battery discharger - will this work?
George - 2009-02-28 10:10:00
The circut is here:
http://drop.io/kuv9yi5
The idea is to discharge a NiMH AA cell at 500ma down to the point
where the cell voltage is 1V. I picked the specific parts because I
already have them in my junque bin.
The idea is that R1 is the sense resistor which should have a
voltage ...Can a capacitor let DC current through?
vorange - 2007-08-19 22:54:00
1st question : Till now, I believed that capacitors only let AC
signals through while blocking DC. But then, I saw a schematic whee
they put a capacitor on the output line of an opamp. The signal into
the opamp was a square wave signal (which I imagine is DC and not
AC). How then does the out...Alternative voltage reference?
MRW - 2007-07-23 14:28:00
Hi! I would like to know if there are other means to setup a voltage
reference. I came up with this circuit:
http://bayimg.com/iAeflAAbg
The purpose is to have a voltage divider (via a potentiometer) where
the output swings from 2.5 to 2V. One way I came up with is by using an
opamp voltage f...How do you derive opamp equations if you flip the opamp in an inverting configuration?
MRW - 2007-02-01 11:17:00
I'm actually curious because when I tried playing around with some
circuit simulation I had accidentally interchanged the inverting and
non-inverting input in an inverting configuration. I knew my output
was funky so I tried doing hand calculations and my equations came out
the same.
??
Than...can an opamp sink current
panfilero - 2009-03-24 20:44:00
can an opamp sink current? I'm guessing yes, since I would guess
there may be some kind of totem pole thing going on at the output and
thats how regular 7400s roll at their output so... since 7400 can
sink, opamps can sink....
????
...How does this circuit work? Is it a pre-amp?
MRW - 2007-07-03 16:58:00
Hello!
Happy 4th of July to my American colleagues!
I have this circuit: http://bayimg.com/NaDlBAAbD
How does it work?
I initially thought that the first opamp is a microphone pre-amplifier
in an inverting configuration and the second one is used to invert the
signal back. But when I l...What do you do with unused opamps in a quad package?
MRW - 2007-07-26 14:01:00
Hi all. I remember posting a question before regarding leaving opamp
inputs open. From what I read, the inputs should be connected to ground
or some voltage source to have some meaningful output.
So, if I used an IC with 4 opamps and only utilized 2 of them, does
that mean that I have to gro...Re: amplifiers
Hammy - 2008-06-25 07:07:00
On Wed, 25 Jun 2008 00:15:35 -0700 (PDT), upasna
wrote:
> the output of an amplifier is a square wave when the input is a sine
> wave.what is the explanation for this?
The opamp output can only swing to the rails or close to it depending
on the opamp.If your output signal is larger the...basic opamp grounding question
panfilero - 2009-03-16 16:59:00
Hello,
If I have an OpAmp (a 741 for example) and I want to use it as a
buffer, and will be sending it 2Vdc, and am powering it with a dual
power supply +/-10V.... do I have to tie the grounds of my input
signal to the grounds of my power supply signal? the 2V ground and
the +/-10V ground?
...Re: a question about resistors in an arc experiment
MooseFET - 2009-01-21 09:25:00
On Jan 20, 8:01=A0pm, John Larkin
wrote:
> On Tue, 20 Jan 2009 17:51:12 -0800 (PST), MooseFET
>
> wrote:
> > > The first one certainly freaks out the opamp by ac-grounding its
> > > inverting input, doing I'm not exactly sure what. It would be stable
> > > for some small cap va...Inverter performance
lerameur - 2008-09-15 10:03:00
Hello,
I made two inverter circuit:
http://www3.sympatico.ca/captoro/inverter.gif
My goal is to have about 33-33v in the output to drive some mosfets.
I am not about which circuit is more stable, the one with OP amp or
the one below with just the Mosfets.
The problem with the CMOS inverter ...Re: Using Frequency to voltage converter. LM2907
vorange - 2007-08-23 22:19:00
On Aug 23, 12:34 pm, John Fields
wrote:
> On Wed, 22 Aug 2007 14:23:20 -0700, alfre...@msn.com wrote:
> > I bought a LM2907 and im trying to build a tachometer for a RC car.
> > I've looked at the schematics and I've tried to test the ic by
> > inputing a pulse of 1Khz , 250mVPP waveform...Re: OP-Amp and A-D Question
David L. Jones - 2009-09-10 02:35:00
RogerN wrote:
> Let's say, for example, I have an Op-amp set up with a gain of 1, if
> I have 2.5V at the - input and 2.7V at the + input, would the output be
> 0.2V
> or 2.7V? If 2.7V, how do you set this up for an A-D converter?
Your example does not make sense.
If the opamp is "setu...op amp basics
lerameur - 2008-05-13 04:20:00
hello,
I am trying to understand the fundamental of op-amp.
I found this link to be very interesting:
courses.ece.uiuc.edu/ece486/labs/lab1/386_op_amp.pdf
I would like to know why that when the output of an opamp is
connected to the input, like a voltage follower, the voltage is equal
to th...unstable opamp ringing oscillating and such
panfilero - 2010-08-11 10:49:00
can anyone in here explain why a OpAmp could oscillate or become
unstable if there are 2 poles before it reaches 0dB on a plot of gain
vs frequency?
Here's what I've gathered thus far... there's a cap internal to the op-
amp, that cap is there for some reason and it puts the dominant pole
in ...Is it okay if I leave an opamp or comparator input open?
MRW - 2007-07-24 22:18:00
I am curious if it is okay to leave an opamp or comparator inverting
or non-inverting input open while the device is powered.
Thanks!
...Re: Creating a voltage-controlled resistance
David L. Jones - 2007-09-12 01:21:00
On Sep 12, 12:56 am, "David" wrote:
> I'm testing rechargeable batteries and would like a voltage-controlled
> resistance so I can easily adjust the load with a program.
>
> I'd appreciate recommendations on how to design this.
>
> Thanks,
>
> David
All you need is a suitable M...Opamp offset voltage problem
2007-02-02 01:36:00
Hi! I want to measure the offset voltage of an opamp. First, I
configure the opamp in an unity gain buffer and measure the output.
The offset voltage is 64.16uV. Then, I applied this voltage to the
non-
inverting input of the opamp. When I simulate it again, instead of
getting 0V at the output,...Re: why do we prefer to supply voltages at the inverting terminal of an op-amp???
Ban - 2006-11-10 03:50:00
archie wrote:
> why do we prefer to supply voltages at the inverting terminal,or
> conventionally known as the negative terminal of an op-amp???
We don't.
Supply voltages are usually something like +/-5V or +/-15V. They are
connected to the positive respective negative terminal of the opam...Weird diff amp behavior?
Sam - 2007-04-08 17:03:00
hey,
i'm using a LM324 opamp configured as a diff amp. the inputs come
from opamp followers, so there shouldn't be any loading issues.
when i vary the input connected to the inverting (-) terminal
everything's fine - i see a clear change in the differential output.
but when i vary the inpu...LTSpice and OpAmp Oscillation
M. Hamed - 2009-05-31 17:22:00
I've built a discrete transistor OpAmp, and when the input was off, I
saw it oscillating. So, I got interested in OpAmp oscillation and
compensation. The main criterion is that a Phase shift of 180 degrees
occur when the loop gain is higher than 1.
I tried to demonstrate that in LTSpice but co...Re: Simple electret "pre-amp"
Lord Garth - 2007-04-30 20:39:00
wrote in message
news:1177978474.155082.237790@e65g2000hsc.googlegroups.com...
> I am using a Logitech/Labtech USB microphone which is doing an okay
> job but could benefit from some more gain. I don't want to touch their
> ADC and USB circuit but would prefer adding something in-line. G...Re: 555 timer chip tone voltage monitor ???
John Fields - 2007-04-02 19:54:00
On 2 Apr 2007 15:14:06 -0700, "twilightzonepinball"
wrote:
> Hello,
>
> My name is Tom and I am new to this group. Please forgive my
> newbieness. I am an Industrial controls tech with limited electronics
> knowledge.
>
>
> I was hoping I could get some help designing a simple tone ...Re: Can someone help me derive the equations for this circuit?
The Phantom - 2007-06-07 10:56:00
On Thu, 07 Jun 2007 13:55:16 -0000, MRW wrote:
> On Jun 5, 9:33 pm, The Phantom wrote:
> > What datasheet is this from?
>
>
> Hi. I got it from:
> http://www.intersil.com/data/an/an9757.pdf
>
> Thanks!
Have you had any luck deriving the equations?
I think I can see where ...Re: Operational amplifiers question...
Jonathan Kirwan - 2006-10-08 18:00:00
On 8 Oct 2006 13:44:34 -0700, a.spears@gmail.com wrote:
> This is a question from my instrumental analytical chemistry text,
> which oviously hasn't helped me. I looked through my physics text but
> it doesn't cover operational amplifiers.
>
> Design a circuit having and output given by -v_o...making a variable -5V to 5V voltage source
panfilero - 2009-03-26 15:01:00
ok... I would like to be able to apply a voltage range of about -5V to
5V across a load, and all I want to do this by varying a 0-10V power
supply..... here's what I'm thinking about doing....
Use two opamp buffers, on one of them I will pass my 0-10V and on the
other I will be passing a 5V re...Re: Electret microphone question
john jardine - 2007-01-16 19:53:00
"MRW" wrote in message
news:1168885085.063760.40050@s34g2000cwa.googlegroups.com...
> Good morning everyone:
>
> I have the following crude circuit on the breadboard:
> http://img116.imageshack.us/my.php?image=micpreampbl4.jpg
>
> The opamps are part of an LM6134 IC. Here is a link...Re: Voltage followers with outputs connected
John Larkin - 2007-01-04 15:41:00
On 4 Jan 2007 10:37:41 -0800, "MRW" wrote:
> Thanks Costas!
>
> Costas Vlachos wrote:
> > MRW wrote:
> > > Happy New Year!
> > >
> > > What happens if I connect the outputs of four opamps configured as
> > > voltage followers?
> > >
> > > I am not sure if I'm applying th...