Op-amp design: Bipolar or Cmos

I had a load cell circuit connected to a servovalve once. It was supposed to be for testing the winches that they use for tightening the wires that hold up radio masts.

On site, you could *hear* the radio program coming out of the hydraulic valve! "This is the BBC..." or somesuch.

At that rate I'd look around and see if I could use a commercially available jelly been part.

The Opamps I've seen on S0Cs so far were IMHO, as Archie Bunker would have put it, lousay.

Many opamps can be purchased as die. Even if the datasheet doesn't say so it is worth contacting the manufacturer about it. If you want to save the bonding and pour it into your chip design you could ask them about a license. I mean, these days they are licensing complete micro controllers, why not a simple opamp? Or maybe Jim has one in the hopper where he owns a right to resale of the IP.

Yes, the reference design says a gain of 10. But we have plenty of silicon spaces for as many stages as we need.

Dice are not good enough. They need to be at exact places of the wafer, and bonding out on the other side.

Yes, how about it, Jim?

I got a free bipolar reference design, so just looking for additional options.

Exactly. Or other noise source, not necessarily modulated in the conventional sense.

Best regards, Spehro Pefhany

I like op amps with that new op-amp smell.. mmmmmmm :) D from BC

LM358 is cool: a decent 741-type dual opamp in SO-8 for around 12 cents! That's 6 cents per opamp!

In my youth, my mentor Melvin Goldstein told me that, some day, transistors inside ICs would cost a penny each. I thought he was nuts.

John

Don't have time to go through it again right now but IIRC even the old Geiger, Allen, Strader "VLSI Design Techniques" had CMOS examples in there. Might have to lay it out but in IC design that is usually done by layouters, not the actual (more expensive) designers.

That's quite expensive...

In my youth we had professors who told us there soon would be only ICs, no individual transistors anymore and discrete HW design would fall by the wayside. We had better not embark on that as a career (which is exactamente what I did anyways). I had to leave the auditorium rather quickly to shake of a major ROFL episode.

Whatever you do, mind the current noise of that charge pump. The PSRR of an opamp ain't infinitely high.

Did Widlar program in C ?:-)

VHDL is NOT IC design.

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

No, probably in more in a "C" like Cuerva (Jose Cuerva) and on his Mexican computer.

Shhht. Don't spill the beans. As long as universities think it is the same then guys like you have it made. For me it's similar, as long as they think and teach that SPICE is analog design.

Of course I meant "Jose Cuervo". A su salud!

But you need 50 cents of wire bonding and packaging, in chip and pcb.

That's just as expensive, especially in learning curve.

We are a nano size company, so the designers and layouters are the same. The IC and PCB layouters also program the uC as well.

LOL! Classic.

Best regards, Spehro Pefhany

Just buy one of the shelf it will be millions cheaper !

Yeah, but capacitors can have bad effects too.. like slowing down the response of your circuit in a desired frequency range or making it unstable so it becomes an oscillator rather than an amplifier. They also cost money and use board space.

Best regards, Spehro Pefhany

I met Widlar's girlfriend at the bar at the Washingtin Square Bar and Grille, in San Francisco. They were living in Puerto Vallarta at the time, and she was back in town visiting family. She was surprised that I'd heard of him... she had no idea how famous he was. She saad that he kept his designs under the kitchen tablecloth and she was not allowed to look. He only worked on them when she was out.

She was concerned that he was drinking too much.

John

If nobody in your company has ever done that, yes. But seriously, I'd use an outside chip designer in that case. We had done the same, although our ultrasound company was about 300 employees.

Those places are often seriously fun to work at. The smaller the better.