fully differential opamp implementation

[tiger66]

The cold end of the resistor going into the + input of the 3rd amp is
the output reference; it need not be ground.

John

Hi John
I tried to implement the circuit in Fig4 of the article "A COMS
Chopper Amplifier" by Christian C. ENZ.

Can you take a look at the circuit diagram. If you can't find it
online, I can email you a copy

Is there something wrong with the amplifier connection because the
circuit shows that all the - inputs are connect to the output and the
+input are grounded? When I simulate, I keeps getting "timestep too
small" error message. I am currently using Multisim.

Thanks

 

[Jim Thompson]

Hi John
I tried to implement the circuit in Fig4 of the article "A COMS
Chopper Amplifier" by Christian C. ENZ.

Can you take a look at the circuit diagram. If you can't find it
online, I can email you a copy

Is there something wrong with the amplifier connection because the
circuit shows that all the - inputs are connect to the output and the
+input are grounded? When I simulate, I keeps getting "timestep too
small" error message. I am currently using Multisim.

Thanks

Why don't you post the schematic to alt.binaries.schematics.electronic
?

We can't see the schematic because it's locked up by IEEE... seeable
by fee only :-(

...Jim Thompson

 

[tiger66]

Why don't you post the schematic to alt.binaries.schematics.electronic
?

We can't see the schematic because it's locked up by IEEE... seeable
by fee only :-(

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

Hi Jim
My circuit can simulate after I flip the amplifier from + to -.

However, I have a new problem with the Sample/Hold circuit design.

I tried to join the newsgroup you posted, but I don't remember my ISP
username/password. So I post a copy of an article with the circuit
that I want to simulate in the following website:
http://www.edaboard.com/forum87.html
My title is Sample/Hold Circuit Problem

Could you check if there is something wrong with the circuit or if
there is something wrong with the values that I use?

I would really appreciate your help

Thanks

 

[tiger66]

I told you before.

It's crap.

Graham

Hi Graham

What tool do you use for simulation?

I don't have cadence. Other simulation tools that I have access to are
student version of Pspice and LTSpice

I don't think LTSpice allows me to plot PSD of a signal. So should I
start using PSpice and give up multisim?

Thanks

 

[Jim Thompson]

Hi Jim
My circuit can simulate after I flip the amplifier from + to -.

However, I have a new problem with the Sample/Hold circuit design.

I tried to join the newsgroup you posted, but I don't remember my ISP
username/password. So I post a copy of an article with the circuit
that I want to simulate in the following website:
http://www.edaboard.com/forum87.html
My title is Sample/Hold Circuit Problem

Could you check if there is something wrong with the circuit or if
there is something wrong with the values that I use?

I would really appreciate your help

Thanks

It says I have to log-in to view the schematic. I log-in for no one.
Go to my website and E-mail me a copy of the schematic.

...Jim Thompson

 

[tiger66]

It says I have to log-in to view the schematic. I log-in for no one.
Go to my website and E-mail me a copy of the schematic.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

Thanks very much Jim...did you get my email?

 

[Jim Thompson]

Thanks very much Jim...did you get my email?

Got it. Will look it over late tomorrow or Tuesday morning, after my
right eye is back operational ;-)

...Jim Thompson

 

[tiger66]

Got it. Will look it over late tomorrow or Tuesday morning, after my
right eye is back operational ;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

Thanks very much Jim..I look forward to hearing from you

 

[Eeyore]

Hi Graham

What tool do you use for simulation?

I've used several versions of EWB (electronics work bench) the predecessor of
Multisim so I've seen this many times too. It annoys the heck out of me. It seems to
do it for silly reasons but usually when you have something that's a bit non-linear
IME.

I don't have cadence. Other simulation tools that I have access to are
student version of Pspice and LTSpice

Not good enough ?

I don't think LTSpice allows me to plot PSD of a signal. So should I
start using PSpice and give up multisim?

It might be a good idea.

Graham

 

[tiger66]

I've used several versions of EWB (electronics work bench) the predecessor of
Multisim so I've seen this many times too. It annoys the heck out of me. It seems to
do it for silly reasons but usually when you have something that's a bit non-linear
IME.


Not good enough ?


It might be a good idea.

Graham

Hi Graham

You seem to have a lot of experience in multisim. Do you still have
the tool?

Can I send you my circuit file and let you take a look and see if you
know where the problems are?
It's not a big circuit.

please let me know

thanks

 

[Eeyore]

Hi Graham

You seem to have a lot of experience in multisim. Do you still have
the tool?

I still have a copy of EWB5. I never installed Multisim itself.

Can I send you my circuit file and let you take a look and see if you
know where the problems are?
It's not a big circuit.

please let me know

What's the file extension ?

Graham

 

[Jim Thompson]

Hi All
I need a fully differential opamp for my circuit design.
Unfortunately, the simulator I use, multisim, does not have a build in
fully differential opamp.

So, I was wondering if any of you have experience implementing a fully
differential opamp, can you please help me to implement one?
Any resources (i.e. netlist, circuit diagram) will be really
appreciated

thanks

See...

Newsgroups: alt.binaries.schematics.electronic
Subject: Fully Differential (from S.E.D) - FullyDifferential.pdf
Message-ID: <[email protected]>

Spice can get cantankerous about "DC path to ground", so the schematic
on A.B.S.E gives paths on both sides of the VCVS.

You may also need some large-valued resistors elsewhere in your
circuit.

Copy also E-mailed.

...Jim Thompson

 

[tiger66]

I still have a copy of EWB5. I never installed Multisim itself.



What's the file extension ?

Graham

Hi Graham
the file extension is .ms7. Would you be able to open the file?

Thanks

 

[tiger66]

See...

Newsgroups: alt.binaries.schematics.electronic
Subject: Fully Differential (from S.E.D) - FullyDifferential.pdf
Message-ID: <[email protected]>

Spice can get cantankerous about "DC path to ground", so the schematic
on A.B.S.E gives paths on both sides of the VCVS.

You may also need some large-valued resistors elsewhere in your
circuit.

Copy also E-mailed.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

Hi Jim
I appreciated your help in fixing my fully differential amplifier.
Unfortunately, the output of my chopper stabilized amplifier is a
square wave which does not match my sine wave input.

You suggested that I "Scope" the outputs of your differential source
simultaneous with your switch drive timing.
Can you please explain this a little bit more. I don't understand what
I need to do


Thanks

 

[Eeyore]

Hi Graham
the file extension is .ms7. Would you be able to open the file?

Not at present. There may be an evaluation copy of Multisim, I'll let you know.

Graham

 

[tiger66]

Not at present. There may be an evaluation copy of Multisim, I'll let you know.

Graham

Hi Graham
Before you get the evaluation copy of Multisim.

Can I send you the screen shot of my schematic and the document with
the circuit that I am trying to simulate?

Maybe you can find my schematic problem just by comparing the two.

please let me know

Thanks so much for helping

 

[tiger66]

Hi Graham
Before you get the evaluation copy of Multisim.

Can I send you the screen shot of my schematic and the document with
the circuit that I am trying to simulate?

Maybe you can find my schematic problem just by comparing the two.

please let me know

Thanks so much for helping

Hi All
I am trying to design a low pass filter for my chopper stabilized
amplifier. Before it's been filtered, the output has a huge offset
voltage. So, I am hoping that after I add the low pass filter to the
output, the offset voltage will disappear.

My input signal is 500Hz, so based on the equation f=1/2*pi*RC, I pick
R=20KOhms and C=16nF. Then I use the oscilloscope to see the output of
the LPF, for some reason, I get a wave form that looks like a HPF
(i.e. it starts from 0 and increases to a steady state value and never
comes down)

Does anyone know what's wrong with my LPF design? I am really stocked
and confused

Please help

Thanks

 

[Lionel]

I am trying to design a low pass filter for my chopper stabilized
amplifier. Before it's been filtered, the output has a huge offset
voltage. So, I am hoping that after I add the low pass filter to the
output, the offset voltage will disappear.

My input signal is 500Hz, so based on the equation f=1/2*pi*RC, I pick
R=20KOhms and C=16nF. Then I use the oscilloscope to see the output of
the LPF, for some reason, I get a wave form that looks like a HPF
(i.e. it starts from 0 and increases to a steady state value and never
comes down)

Does anyone know what's wrong with my LPF design? I am really stocked
and confused

Sounds like you have your cap in series with your signal, & your
resistor going to ground, instead of the other way around. Swap them &
it should work. (I'm assuming that your LPF is a simple RC
combination, rather than part of a feedback loop for an opamp.)

PS: When posting in a thread like this, please try to snip out the
quoted material that's unrelated to your own comments. Doing so makes
it a lot easier to understand a person's posts. :^)

 

[Eeyore]

Hi Graham
Before you get the evaluation copy of Multisim.

Can I send you the screen shot of my schematic and the document with
the circuit that I am trying to simulate?

Maybe you can find my schematic problem just by comparing the two.

Please do that. The hotmail address in my headers does work.

Graham

 

[Eeyore]

Hi All
I am trying to design a low pass filter for my chopper stabilized
amplifier. Before it's been filtered, the output has a huge offset
voltage. So, I am hoping that after I add the low pass filter to the
output, the offset voltage will disappear.

You need a high pass filter for that.

Graham