microcontroller with built-in op-amp

address is fake.)

There are a few but performance is usually somewhat compromised compared to an external amp.

Some of the micros with delta-sigma ADCs have PGAs built in that would be suitable for that sort of application.

Best regards, Spehro Pefhany

Check out Cypress' PSOCs. They have field-programmalbe analog gate arrays with zippy little MCU attached.

Noel

Hi Robert, look at

Andreas

You can also do this using a DAC, and an increasing number of mixed signal uC now also nclude DACS - see MSC12xx from TI, most SiLabs C8051Fxx series, some Philips LPC series (etc).

-jg

Not a great idea to amplify such a low level signal inside a micro banging the rails with digital noise. Your signal to noise ratio will be huge.

You are better off amplifying with an external op amp, with a good board layout to minimize noise floor. Then feed that into a micro with A2D inputs.

The PSoC fits the bill. BUT the Op-Amps and the analog have limitations. It may or may not work in your application.

The Zippy little MCU is limited by the weak C compiler. ( code is a little big and the ROM is a little small) (I am told ASM is OK) No bit operands. the Development environment has a big learning curve.

It is good for many things, But not all.

address is fake.)

A microcontroller on a chip is a too noisy friend to low-level analog signals, like strain gages.

Could you think the other way around: take an external very good A/D and use it on the bridge directly?

For examples, get Linear Technology LTC2420 data sheets and application notes.

Take a look at the UTI (Universal Transducer Interface) from Smartec

Meindert

Thanks to all of you for your very thoughtful comments and suggestions. Now I must digest it all to see what it means for my application, which is a body-mounted humidity logger for a medical research project.

-Robert Scott Ypsilanti, Michigan (Reply through this forum, not by direct e-mail to me, as automatic reply address is fake.)

True. But amazing things have been done with them.

I stick with assembly. I've been burned by c compilers in the past when code and data spaces are limited.

I agree.

Noel