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
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
I mean micro power 'cause it's not a power amp I need, 1mA or so is just ok for the application.
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.
Best regards, H
This bootstrapping trick might do what you want with a fairly normal part and a few discrete components to handle the voltages.
Cruder versions are available. For once EDN comes good :
How close to rail to rail it is depends on your choice of opamp.
-- Regards, Martin Brown
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
This is my minimalist HV amp:
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. Claude Bernard
Fluke used the second idea in their 5200 ac calibrator output power amplifer. Neat bit of circuit design...
Chris
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
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
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.
Sure. Do it all right.
Do you need isolation?
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:
-- John Larkin Highland Technology, Inc trk The cork popped merrily, and Lord Peter rose to his feet. "Bunter", he said, "I give you a toast. The triumph of Instinct over Reason"
Cascoding into a bipolar emitter is better for the bandpass.
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.