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Op-amp
Sci.Electronics.Design is a worldwide Usenet news group that is used to discuss various aspects of Electronic Circuit Design.
We found 560 threads matching "opamp"
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The most relevant threads are listed first
power opamp?
John Larkin - 2008-03-02 16:04:00
What's a good medium-power opamp? I need to source/sink at least 60
mA, with say +-7.5 volt supplies, and swing +-6 maybe. No particular
requirements otherwise.
I suppose I could boost a cheap SOT-23 opamp with a couple of cheap
SOT-23 emitter followers....
...
Re: IGBT and MOS in a linear regulator
Jan Panteltje - 2009-05-08 11:17:00
On a sunny day (Fri, 08 May 2009 14:02:01 GMT) it happened "maxi"
wrote in
:
> Ok, is in a serie configuration
>
> Here the diagram:
>
> http://it.tinypic.com/r/aweqvm/5
Interesting, not sure I would do it that way, maybe I do not understand it?
...How to choose the right opamp
2008-11-23 03:42:00
Hi,
if i consider a signal with a defined bandwith, how can i choose the
right opamp to amplify it?
For example, if consider a signal with a maximum frequency of 1kHz i
think i should use an opamp with first pole equal or greater to 1kHz:
is it right?If so, what is the phase effect on the real ...Output range of an opamp
2008-10-02 15:23:00
I have made an opamp and i would calculate its output range in spice.
I have non idea how to do it in accurate and precision way without
confusing output range with icmr. I've found as method an inverting
configuration with feedback gain greater than one: with this method my
opamp have a certain...Re: OpAmp Input Resistance
John Fields - 2010-08-24 21:18:00
On Tue, 24 Aug 2010 15:10:22 -0700 (PDT), panfilero
wrote:
> When does the really high input resistance of the OpAmp go away? .....
> I remember the 3 OpAmp Instrumentation amplifier.... and I believe I
> recall the final stage OpAmp being a differential OpAmp, and that it
> had a low inpu...Turning off the LM395.
George Herold - 2010-08-19 11:08:00
The following simple single supply op-amp with transistor power
booster won=92t go down to zero. With the input to the opamp at zero
the output from the opamp is at 20mV and the emitter of the LM395 is
at 0.6 volts.
(V+)---------------+
|
|
|\ ...Opamp wanted
Bearplug Bearplug Bearplug - 2009-09-07 05:45:00
I need a single/dual opamp for an audio buffer stage in a DIP-8 package.
Pinout is flexible, supply is +/- 18V. It has a drive capability similar
to NE5534/5532, but with FET input. Availability from Digikey or Mouser
and low cost a plus.
Suggestions? TIA.
Regards,
b
B
...Current Sense Opamp Circuit Problem
jdhar - 2008-10-22 15:36:00
I have implemented a slight variant on the circuit in this datasheet,
Page 21, Figure 69:
http://www.analog.com/static/imported-files/data_sheets/AD8551_8552_8554.pdf
The problem I am having is that as I lower the voltage at the node
Rsense/R1 are connected to (lets called that Vreg), and in...Question about opamp design
2008-10-22 06:22:00
I should design an opamp transimpedance amplifier as homework, but i
have some doubts:
1) if current signal is an impulse (of positive value) generated every
10ms (for example), is it right to put the first pole of open loop
gain at frequency higher than (1/10)KHz?Or i shoud put the first pole
...SPICE opamp model with adjustable slew-rate
2008-03-11 10:09:00
Hi.
I want to examine the effect of limited slew-rate (real) opamps that I
use in diode rectifiers as part of asynchronous amplitude
demodulators.
Therefor I'm searching for a (spice) opamp model with adjustable slew
rate.
The ideal model "opamp" of PSpice has adjustable Gain-Bandwidth-
...opamp differential amplifier high frequency/loading effect
krishmaniac@hotmail.com - 2007-12-21 06:11:00
Hi,
I have a simple difference amplifier based on an opamp. I have few
issues related to its deisgn and analysis.
I have to design it for a differential gain of 10. The gain is decided
by the ratio of the resistors used. R2/R1=R4/R3=10. Normally, what is
the guidelines to select range of resist...CMOS OpAmp Design
2008-12-16 02:29:00
Hi,
I was looking for a CMOS OpAmp circuit which doesnt need need any
special Common Mode Feedback circuit for stabilizing the bias point.
Anybody has come across a circuit like that ?
Please let me know
regards
Jean
...Transimpedance amplifier
2009-01-11 17:49:00
Hi,
i've simulated a transimpedance amplifier with spice. My circuit is
composed of an opamp and a feedback resistor; in parallel to current
source a capacitor is present (i want to use a photodiode's equivalent
model). I have a question: is it possible that (with an ac sweep), V/I
transfer fun...OpAmp Q:
krw - 2009-01-19 10:04:00
Question from a too-long digital type: Given a run-of-the-mill
voltage feedback OpAmp (e.g. LM833) is there a benefit of certain
ranges of resistor values, other than the obvious (bias/offset
currents)? ...like stability? I was trying to save supply
current, but that requirement was b...LTC6240
Vladimir Vassilevsky - 2007-12-30 16:15:00
I am fighting with the LTC6240 opamp. This is a remarkable opamp
because of the bipolar-like voltage noise and the FET-like current
noise. There is a lot of weirdness in the specs:
* Current noise is increased with the frequency
* Gain/Phase plots are not monotonous
* It does not ...Re: Not attaining required slew rate on differential ADC input buffer
Nicholas Kinar - 2009-12-28 14:55:00
>
> One caution: most modern ADCs kick out a big zot of charge when they
> digitize. If an opamp is connected directly to the ADC, some opamps
> get seriously freaked out by that zot and take a long time to recover.
> Hence the RC after the opamp. But the values have to be right; too
> ...Buffered Opamp
2008-09-17 02:50:00
I'm studying buffered opamp and i've found this configuration
http://img156.imageshack.us/img156/5640/afsdafen7.png
i don't understand second statement
"reduces output load at the drains of M6 and M7"
I don't understand why a large resistance at the drains of M6 and M7
is a bad thing...if i con...Negative PSRR in two stage opamp
2008-09-25 14:05:00
I have problems to simulate negative psrr in two stage opamp...
If i consider an ac Vss in series with a dc VSS, if opamp is
configured as buffer with V+ to ground, i should have Vout/Vss=1/
Psrr-, so Psrr-=Vss/Vout.....is this right?
I've simulated this configuration in spice with dc VSS=2V and...Audio Blending Between Opamps?
Brandon - 2008-05-15 21:22:00
Hi everyone. Let me start off by saying that I am a hobbyist when it
comes to electronics so hopefully this question won't sound too
stupid. In a little audio project I am working on, I am using two
opamps (one dual opamp actually) as buffers for incoming audio
signals. I want to blend the ou...Re: Pic temp sensor
John Larkin - 2008-02-22 12:04:00
On Fri, 22 Feb 2008 07:21:52 -0800 (PST), Pj
wrote:
> What would probably be the likely cause of the output bouncing on the
> lower 4 bits, bits 0,1,2,3, but has good stability on the upper bits.
> I'm using a junk box Pic 16f807 with one input line to AN0 which is
> being fed from the out...Re: voltage limting problem
john - 2008-05-15 11:17:00
Hi,
The thing is that my application needs full VCCS current to go into
the Load and the Opamps should only be monitoring the voltage across
the load and the capacitor in series. The opamp usually have very
impedance input. How much controlled current do you think opamp needs
to operate pro...3.3v robustness
Daveb - 2008-11-02 04:00:00
Hi,
Does anyone have any experience/thoughts on the robustness of a 3.3v
CMOS Opamp configured as a differential amp with the inputs connected
via 10m cables to a strain gauge bridge in an electrically noisy
environment ? If I add clamp diodes from the opamp inputs to the rails
is there any d...Re: a question about resistors in an arc experiment
John Larkin - 2009-01-20 23:01:00
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 values.
>
> It would depend a lot on the op-amp. It is very...Re: Parts per million / LSB
john - 2008-09-02 14:51:00
Hi,
I have one more question that in chapter 4, the note disscuss how to
design a opamp system using the four different combination of linear
equation
Y = mX + B,
The author suggests the linear equation, defines the input and output
voltages and then draws the circuit. My questions a...Re: Maintaining a Vbe Multiplier's bias value
Jon Kirwan - 2010-02-11 03:24:00
On Wed, 10 Feb 2010 19:55:44 -0800 (PST), George Herold
wrote:
> I'm perhaps more of a novice than you...
Somehow, I doubt that. I barely rate "hobbyist."
> but I find opamp circuits complicated enough....
Don't sweat it. While some opamps leave _some_ issues nearly
ignorable, the...Re: (V1 + V2) - (V3 + V4) from one op amp ?
Jon Kirwan - 2009-07-29 19:04:00
On Wed, 29 Jul 2009 15:24:24 -0400, Steve wrote:
> I need to use op amps to determine the difference between two summed
> voltages. The summed voltages will be (V1 + V2) and independently (V3
> + V4). The net result needs to be (V1 + V2) - (V3 + V4). Can this be
> done using one op amp ?...Problem with this opamp
2008-06-05 13:41:00
I don't find correct Req value in this opamp configuration:
http://img46.imageshack.us/img46/1848/opampnr3.png
If i don't consider Ib and define:
1)Va=voltage across R2
2)eo=Ip*Req
Va=RfT*Ip=(R2/(R2+R1))eo, so e0=Ip*(RfT*(1+R1/R2))
This result is right if Rft> > R1, but in general Req=Rft+R1+(...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 ...Re: Hoorah for the patent system
John Larkin - 2008-01-11 19:17:00
On Fri, 11 Jan 2008 15:57:50 -0800 (PST), MooseFET
wrote:
> On Jan 11, 7:49 am, John Larkin
> wrote:
> [... multiple references ...
> > I thought of that, but the lowpass filters must include at least one
> > opamp per, and those opamps will have ballpark 1 nV/rthz noise too.
>
> ...Re: 431 shunt regulator help
Jim Thompson - 2009-02-18 12:16:00
On Tue, 17 Feb 2009 20:16:54 -0800 (PST), Jim
wrote:
> trying to drop 12 vdc to 5vdc for an extended scale A/D, I would like
> to use a TI431 to sense anything above 9 or 10 volts, feed it into my
> uC for display on a digital meter. I am a software guy with limited HW
> experience so he...Re: Infrared LED / detector design
Jan Panteltje - 2010-02-19 17:28:00
On a sunny day (Fri, 19 Feb 2010 13:06:07 -0800 (PST)) it happened Matt
wrote in
:
> FWIW, I did search for quite some time for a data sheet.
>
> Radio Shack
> Model: 276-142
OK, that is just an (any?) IR LED and photo transistor.
You could use a 74HC4046 or even a 555 timer to ...Fast FET opamp from AD
2008-12-11 22:43:00
Mostly this is for Phil Hobbs who was lamenting the demise of some low
noise, low capacitance, fast opamp in a previous post. I received
some email today that led me to order samples of the following,
http://www.analog.com/en/amplifiers-and-comparators/operational-amplifiers-op-amps/ada4817-1/...Phase compensation
2008-11-01 06:46:00
I have some doubts about phase compensation.....
I'm reading Graeme book about transimpedance amplifiers with opamp:he
puts a zero of feedback function at frequency with 0dB loop gain. So,
supposed that 2 first poles (open loop gain of opamp and pole of
feedback loop) are totally evolved, he obt...Re: Problem with simple OpAmp Circuit, need help
Wanderer - 2010-07-14 16:40:00
On Jul 14, 2:54=A0pm, "Jacques St-Pierre"
wrote:
> "Wanderer" wrote in message
>
> news:4ecb4dea-3df5-4050-996a-d3433713895a@d8g2000yqf.googlegroups.com...
> On Jul 14, 11:23 am, "Jacques St-Pierre"
> wrote:
>
> > When you say you power the circuit from a separate supply are...Re: Voltage offset
Mook Johnson - 2008-03-07 09:22:00
wrote in message
news:a9126cbf-5f7d-47e8-bf57-9e7d01175534@34g2000hsz.googlegroups.com...
> I want to read a voltage on a ADC that only accept 0-5V. My input
> signal is 12Vp-p (-6 to 6). I simulate this circuit and it work. I
> have 0 to 4.45V on Vout. My question is, do this circuit ...Bob Pease and opamp-modelling
Candide Voltaire - 2009-04-07 04:41:00
I came across the following article by analog guru Bob Pease
concerning real opamp behaviour:
http://electronicdesign.com/Articles/Print.cfm?ArticleID=3D20565
Unfortunately the article is printed/edited badly, which makes it hard
to understand what Bob is trying to tell
e.g the first formula sh...Re: Standard non-inverting opamp with a cap across + and - terminals...... Why?
John Larkin - 2009-04-13 20:39:00
On Mon, 13 Apr 2009 19:10:55 -0500, Vladimir Vassilevsky
wrote:
>
>
> John Larkin wrote:
>
> > You get 1 mV RMS in a 50 ohm environment from 20 nanowatts of RF. In a
> > higher-impedance, maybe accidentally resonant circuit, one nanowatt
> > can make a millivolt.
>
> Yet gettin...Re: Electronic load advice
mkaras - 2008-02-03 00:34:00
On Feb 2, 5:46 pm, Richard Henry wrote:
> I need to test some battery packs. We predict the load of the target
> product will cycle from high power (80 W for 10 ms) to low power (5 W
> for 240 ms) during operation. I would like to simulate that load
> including the dynamics in the batte...Re: Opamp wanted
Bearplug Bearplug Bearplug - 2009-09-10 10:37:00
Date: Tue, Sep 8, 2009, 11:42pm From: whit3rd@gmail.com (whit3rd)
On Sep 7, 2:45=A0am, Id...@webtv.net (Bearplug Bearplug Bearplug) wrote:
> > I need a single/dual opamp for an
> > audio buffer stage in a DIP-8
> > package. Pinout is flexible, supply
> > is +/- 18V.
> Buffer? ...Standard non-inverting opamp with a cap across + and - terminals...... Why?
mook johnson - 2009-04-07 20:58:00
I was reading some motor drive literature and ran across some motor drive
circuits showing how they filter the motor voltage and corrent signals
before going to the A2D inputs.
They had a standard noninverting opamp (Av=10) with an input bias matching
resistor on the + terminal and a cap (....