dual opamp & negative voltage

Are you sure you mean an LM328. That contains a positive step down voltage regulator. Not sure what a buffer is going to do for you; you need to power it from somewhere.

Tam

Do you mean to say you need more current on the RS232 Interface, or are you trying to use the RS232 signal and/or handshaking lines to power something else?? Please clarify.

Also, I believe a "truly compliant" RS232 device would have to output

-7 volts to -15 volts, and +7 to +15 volts. Everyting in-between is "no-man's land". I'm pretty sure I remember reading that in the RS232 book, but I also know most receivers these days will work to half that number and below.

Why do you need more current?

With out knowing your connections. I'll guess. You have connected the op-amps to the 5 volts + that supplies the MAX chip ? if so, that is all you'll get is 0..5 volts. in order to get a -5 volts out, you need the op-amp to operate from a +/- dual rail with respect to common.

if you look at the MAX chip, you'll notice it has an inverter on it to give you the +/- rails for the chip it self internally. This current is just about enough for the standard specs. but all is not lots how ever! :) if you're operating from a single supply which I think you are ? You can put one of your own little inverters on board. either construct an osc via a higher wattage simple op-amp that can drive a cap and be rectified for a - Volts or, get one of those ready made DC-DC inverters capable of the current you need.

Oh don't go there unless you want the young engineers to attempt chopping off your weenie when you state the proper output voltages for 232 as they should be from years ago. Of course, many are use to the marketing schemes used these days to cut corners and end up getting serial ports on devices that barely output 5 volts..That saves on parts for devices that don't have the supplies internally for the proper voltages like laptops etc..

so there you go!

Glad to see that some one knows the difference. also, the other problem is current. it use to be that 20 ma's was the max output before fold back.. now, it seems that 20 ma's is what you get at short circuit in many implements.

oh well.. It's all falling apart in a hand basket!