Circuit Wanted: Half-Wave Signal Generator

Yeah, that's the obvious choice, except that it puts out a square wave, unless I pick off the capacitor voltage, or integrate the output, both of which I've thought about. Thanks.

Well you said any wave shape: I'd go with Ken on this, but, I'd use a 74HC122 or 74HC123. You can filter the output with an RC (integrator) or CR (differentiator) network, but, if you want to drive a further stage you will probably need an op amp after the filter to get the drive current back.

Yeah - I was trying to avoid a buffer stage, but it may come to that if I can't find anything else. Thanks.

A silicon rectifier inserted into the alternating current used for generating the waveform may be all that is needed. Cost, about £0.04 Sterling.

Can you expand on this a bit? I thought you guys used €.

I think the simpliest way is a schmittrigger oscillator, i.e. 74HC14 and one resistor and one capacitor. Pulstime is about 0.7*RC. If R = 1 MΩ and C = 10 μF, the pulstime is around 7 s. The shape is symetical square.

Anders

I guess I should have been more careful in my description. I don't care about the waveshape, except it needs to have a rise and fall time that covers the entire period - i.e., not a square pulse, but something like a sine, a triangle, etc. I'm going to use this to drive a PWM circuit and I want the PWM to ramp smoothly from 0 to 100% and back to 0.

Thanks.

http://www.maxim-ic.com/appnotes.cfm/an_pk/3201

Use this circuit plus the top half again (triangle output) at much lower frequency to drive the VIN. Use a monostable/multivibrator with clear to drive the VCC input at the top of R3. You'll need one more op amp (in comparator mode) to detect the bottom of the ramp and clear the monostable.

Or use a D type flip flop instead of the monostable: depends what you're doing.

Thanks. I'm a big fan of Maxim/Dallas.

ooh - me likey. Thanks!

Hello "bhankiii,

Now I have a better spec of your problem. I think you can do this for a cheap coin. You can use a CMOS inverter as CD4069 and build a square wave generator and then integrate the signal to a triangular wave in the same IC. The number of components are now three resistors, two capacitors and one (1/2) IC.

I have test to insert a picture of the schematic in this frame, but fail. If you are interested of this, you can mail to g.a.gustavsson@tele2.se .

Anders

Thanks, I'll take a look at this.

"but I thought I'd ask the mob. ". I am not a linguistic but the word "mob" in my view is pinching one. You would had a better chioce.

Regards