High Voltage op amp

Do you have a question? Post it now! No Registration Necessary

Translate This Thread From English to

Threaded View
Hi all,

I need a micro power, op-amp with single supply [0...60V .. 70Vmax], I  
need this for a specific test equipment for batteries, I found the  
LTC2057 which would fulfill my requirements.

I appreciate if someone could give me an advice about this kind of micro  
power high voltage op-amp or may be pointing me to another chip.

Best regards, H

Re: High Voltage op amp
On 06/09/2020 10:53, habib wrote:
Quoted text here. Click to load it

The LTC2057 draws 0.8 - 1.2mA when active. It is only micro-power when  
shutdown.

Can you say more about your requirements: Vos, Ib, GBW, Iq, CMR, does Iq  
need to be low at all supply voltages?

piglet


Re: High Voltage op amp

Quoted text here. Click to load it
I mean micro power 'cause it's not a power amp I need, 1mA or so is just  
ok for the application.
Quoted text here. Click to load it
It just need to be a op-amp with rail to rail output, no specific  
requirements for parameters Iq, CMR, GBW ... etc. No stability for  
output capacitance is needed.
Quoted text here. Click to load it
Best regards, H

Re: High Voltage op amp
On 06/09/2020 10:53, habib wrote:
Quoted text here. Click to load it

This bootstrapping trick might do what you want with a fairly normal  
part and a few discrete components to handle the voltages.

https://www.analog.com/media/en/analog-dialogue/raqs/raq-issue-168.pdf

Cruder versions are available. For once EDN comes good :

https://www.edn.com/bootstrapping-your-op-amp-yields-wide-voltage-swings/

How close to rail to rail it is depends on your choice of opamp.

--  
Regards,
Martin Brown

Re: High Voltage op amp

Quoted text here. Click to load it
Good ! Boostrapping from op amp output is one of ideas I did not  
remember, thanks.

Single supply [0..60V .. 70Vmax] is a requirement.

Unfortunately my design shall become complicated if I design symmetrical  
power supplies for the analog blocks of the test bench, nevertheless I  
will see if it is possible.

Thanks for the idea, H

Re: High Voltage op amp
On 09/06/20 13:28, Martin Brown wrote:
Quoted text here. Click to load it

Fluke used the second idea in their 5200 ac calibrator output power
amplifer. Neat bit of circuit design...

Chris


Re: High Voltage op amp
wrote:

Quoted text here. Click to load it

This is my minimalist HV amp:

https://www.dropbox.com/s/w8px8z9mf64wpc9/HVamp.JPG?raw=1

With a little tweaking, the opamp supply current can be made
arbitrarily low. The output can be run pure class-B, so the only
current there is whatever the load needs.






--  

John Larkin         Highland Technology, Inc

Science teaches us to doubt.

We've slightly trimmed the long signature. Click to see the full one.
Re: High Voltage op amp
On Sunday, 6 September 2020 16:31:56 UTC+1, snipped-for-privacy@highlandsniptechnology.com  wrote:
Quoted text here. Click to load it

Putting opo-isolator LEDs in the supply rails of an op-amp and loading
the output with a resistor is a very neat trick.  I first came across
it in a Burr Brown linear opto-isolator hybrid module in the late 1970s
but it may well be much older than that.
The data sheet of the isolator module does not even hint that this
is how it works, but I dismantled a broken one to find out how
they did it. I could dig out the part number if anyone is interested.

John

Re: High Voltage op amp
On 09/07/20 11:19, snipped-for-privacy@gmail.com wrote:
Quoted text here. Click to load it

Neat idea, but stability of the output stage quiescent current and
power dissipation might be an issue.

Also, need some way of closing the loop back to the op map, so
another opto isolator ?...

Chris



Re: High Voltage op amp
On Monday, 7 September 2020 14:49:20 UTC+1, Chris  wrote:
Quoted text here. Click to load it

That is exactly what they did.
Two optical cavities, each containing an LED and two matched photodiodes.
One photodiode in each cavity provides feedback to the driver op-amp and
the other photodiode is on the other side of the isolation barrier.
One optical cavity for positive signals and the other cavity for negative.
The overall result was reasonably good dc stability and linearity.
Bandwidth was several kilohertz.  I once combined these with audio
transformers to make a multi-channel medical isolator with a linear
phase response from dc to well beyond 20kHz.  Probably around 50kHz.

Re: High Voltage op amp
On Mon, 7 Sep 2020 09:17:08 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

Quoted text here. Click to load it

Sure. Do it all right.

Quoted text here. Click to load it

Do you need isolation?  


Quoted text here. Click to load it

I've also used lower voltage optoisolators with power mosfets in a
totem pole. You can cascode into depletion fets.

There's a logic version too:

https://www.dropbox.com/s/cr5pdtk0s9gilee/Opto_Totem.JPG?raw=1




--  

John Larkin         Highland Technology, Inc   trk

The cork popped merrily, and Lord Peter rose to his feet.  
We've slightly trimmed the long signature. Click to see the full one.
Re: High Voltage op amp
On Monday, September 7, 2020 at 9:41:23 AM UTC-7, John Larkin wrote:
Quoted text here. Click to load it




Cascoding into a bipolar emitter is better for the bandpass.

Site Timeline