Hello,

I am looking for an op-amp circuit to convert a bipolar signal say(+/-10v, sine-wave) to unipolar(half-sinewave of 0-10v). I don't want to build a half-wave rectifier, neither I want to use any diodes.

Can you point me to web-site or circuit diagram?

TIA,
Vasu

national semi has a good appnote on Opamp Applications
about 20-50 different circuits for different uses

(ok I haven't even looked at it for 7 years but If I wanted an opamp circuit like that, thats where I'd look..
I'm assuming you want the circuit that uses a 741 type opamp + some resistors for this.. right?

to be clear what you really want is
V(out) <+ V(in)/2 + 5.0;

NO rectification.. just a little attenuation + shift the midpoint from 0v (midpoint between +10 and -10 to +5v (mid point between +10 and 0v)
right?

OK, looked at the word.doc attachment --

some questions:

integrated or board level design?
(the voltages are big, but there are 60V tolerant CMOS processes out there.)

what frequency is the sinusoid?
(the approach is different at 60Hz and 20GHz)

Some compartors and MOS switches are viable. Also as suggested before, both TI, National and others have lots of application notes on function circuits.

by now you should have already found this..
www.national.com
application note AN-20
jbd

Dear David and Jdb,

The reason which prompted me to do this design is this, I was playing with a function generator and I found that it generates +/-10v sine-wave and using a potentio-meter, it changes that wave-form to unipolar 0-10v with same amplitude range.

One way to do the same is: using a switch, which will allow to change the -VEE of op-amp(make it single supply) but I don't know whether this is normal practice implemented in a function generator and other circuits.

Any pointers will be helpful.

Thanks,

Once upon a time I worked on a project with 128 analog measuring points, and we used a signal conditioning circuit per measuring point to convert the parameter we were measuring (temperature, voltage, current .. etc) into the voltage range of our ADC circuit.
To give you an idea of how long ago this was, we used several chips to build the ADC itself.. (comparator, R2R chip, and SARDAC ) so we only had 1 input range to use.. and that did not accomodate negative voltages, so while there were a couple of voltages we could measure directly (ie no conditioning) many needed inversion and or scaling..
Today I'd look at using a GP Data Aquisition System (on chip) and only have special conditioning circuits..

But ONE idea you might consider would be to do the clipping in post processing..
accept the +/-10 input signal, convert to 2's complement out put data, and then do a simple latch that reads the input data if the sign is NOT set, and uses 0's if the sign bit IS set..
(that could even be in SOFTWARE or firmware!!)

Otherwise I'd have a separate amplification /rectification circuit before the mux - and I think I would probably use the diode unless I had to build 2 million units.. and then I don't know what I'd do, but who ever wanted to build 2 million units would be willing to pay me good $$ to figure out how to reduce the parts count.. and I would.
and I'd spice it, and breadboard it 20 time, until I figured out how to get rid of the diode..

accuracy, speed, cost, development time, power -
pick any three

Hello,

Please explain me the role of R15 in the attached function generator diagram. Can that part could be used for generating a half-cycle.

Thanks,