I just spent the best part of an afternoon bread boarding circuits that I found on google for function generators, about 6 in total, non of which work!!!! I even bought a kit that used the XR2206 which I could get no more than 200mV
pk to pk, I have since read that many of the XR2206 chips used in the kits are manufactured in China and are of dubious quality so I am looking to use op amp circuits.

I am looking to build a function generator into a power supply I am putting together, I don't need anything grand or
glamorous, just a circuit that will give me sine and square wave from around 0.1 Hz to around 20Khz, the lower frequency will be used for logic circuits, counters etc, the sine wave will be used to play with small signal
amplifiers hence the audio frequency range.

Has anyone here got a circuit they wouldn't mind posting please?.... one that works obviously along with
a suitable power supply for said circuit?

 

Square wave in that range is easy. You could use a 555 which has the benefit of being able to drive up to 200mA directly, or a simple op-amp circuit. Getting a sine wave is considerably more complex.

Why not use an app on a smartphone? Hugely more versatile and very precise. Free, once you have the phone.

 

That's not so much fun...I want to build one myself.

Square wave in that range is easy. You could use a 555 which has the benefit of being able to drive up to 200mA directly, or a simple op-amp circuit. Getting a sine wave is considerably more complex.

Why not use an app on a smartphone? Hugely more versatile and very precise. Free, once you have the phone.

 

That's not so much fun...o want to nuold.ome myself.

Fair enough. How accurate do you want frequency-wise and how close to a pure sine? (I cannot help with either, but the experts here will need to know what you want. )

 

Actually id be happy with a high quality sine at 1Khz....I don't need to adjust it, 1 KHz would do me fine as long as the purity is nice

 

I like this one:

The opamp is 1/2 TL072, power supply is ±10V

Output spectrum (2nd harmonic down 50 db, 3rd harmonic is down 45 db):

Vertical: 10 db/division; Horizontal: 1.25 kHz/division.

 

Thanks Dick....how do I power this circuit from a 9v supply? I need to split the 9v rail somehow?

 

Have you thought of trying the "Banggood DDS function generator kit" It looks to be a good design.

Les.

 

Have you thought of trying the "Banggood DDS function generator kit" It looks to be a good design.

Les.

Thanks Les but that's probably overkill for what I need.

 

I'm going to build Dicks circuit when I get a few minutes for my 1Khz sine, then use a 555 for my logic pulse supply.

 

You can use the other half of the tL072 ti make a synthetic ground, but for a tL072, 9v is not much.

The negative terminal of the battery becomes -4.5 volts and the positive terminal of the battery becomes + 4.5 volts compared to the opamp's output. I suggest that capacitors be added from the +4.5V and -4.5 volt outputs to "VGND". I probably don't need to tell you that the -4.5 volt (battery -) should not be connected to ground. Be prepared to ass another battery in series with the first 9V battery if you cannot get a nice output with only ±4.5 volts.

 

Thank you Dick.

 

Here is a $ 4 low end board that does func gen.

https://www.hackster.io/PSoC_Rocks/low-cost-dds-function-generator-for-makers-432d1d

This project could be modified to do ramp as well.


Then there is a higher ended board, $ 10, that has Wavedac component.
Can produce any waveshape you want, for example Ramp, quite useful
in a power supply. You would use A/D to read the pots to control amplitude
and freq. Or control over Bluetooth or UART from PC via Python. Use other
DAC in part to control PS output V and I. Possibilities quite broad, start
simple and code up part over time with additional features. Note this board
does not have Bluetooth, you would use a different board for that.

http://www.cypress.com/documentatio...oc-5lp-prototyping-kit-onboard-programmer-and




Regards, Dana.

 

Ok I knew I was going to get In trouble....I feed the op amp that I am going to use to make my split rails with 9v right? Then I don't know how to configure the output into the circuit that is going to make my waveforms for me, somewhere I need to find 4.5v then where do I apply this 4.5v to....these split rail things have always confused me and probably always will lol

 

+4.5V goes to TL072 pin 8 and -4.5 goes to TL072 pin 4.

 

I just spent the best part of an afternoon bread boarding circuits that I found on google for function generators, about 6 in total, non of which work!!!! I even bought a kit that used the XR2206 which I could get no more than 200mV
pk to pk, I have since read that many of the XR2206 chips used in the kits are manufactured in China and are of dubious quality so I am looking to use op amp circuits.

I am looking to build a function generator into a power supply I am putting together, I don't need anything grand or
glamorous, just a circuit that will give me sine and square wave from around 0.1 Hz to around 20Khz, the lower frequency will be used for logic circuits, counters etc, the sine wave will be used to play with small signal
amplifiers hence the audio frequency range.

Has anyone here got a circuit they wouldn't mind posting please?.... one that works obviously along with
a suitable power supply for said circuit?

Power supply not a

I just spent the best part of an afternoon bread boarding circuits that I found on google for function generators, about 6 in total, non of which work!!!! I even bought a kit that used the XR2206 which I could get no more than 200mV
pk to pk, I have since read that many of the XR2206 chips used in the kits are manufactured in China and are of dubious quality so I am looking to use op amp circuits.

I am looking to build a function generator into a power supply I am putting together, I don't need anything grand or
glamorous, just a circuit that will give me sine and square wave from around 0.1 Hz to around 20Khz, the lower frequency will be used for logic circuits, counters etc, the sine wave will be used to play with small signal
amplifiers hence the audio frequency range.

Has anyone here got a circuit they wouldn't mind posting please?.... one that works obviously along with
a suitable power supply for said circuit?

The power supply is not a problem. Use a circuit using lm317 and lm337. It is ajustable and works 100%

 

Thanks Stupid .... True I did overlook the obvious but that being said, if I take the easy way out every time, then I won't learn too much

 

But the op amp I use to split the supply rail?..... Doesn't that also need a split supply?

 

But the op amp I use to split the supply rail?..... Doesn't that also need a split supply?

No.
Both op amps are connected to the 9V plus and minus (neither end grounded).
The pseudo-ground at the mid voltage point (which can now be the circuit ground) is generated by the one opamp, which is used by the other op amp to generate the sinewave (with it's output centered around the pseudo-ground).

 

Does anyone have time to make a sketch?..... I'm too stupid to understand what is going on here and this is driving me nuts?