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6 March 2010
Author: Giorgos Lazaridis
High Frequency Function Generator with the Maxim MAX038





Worklog - The circuit (March 6 2009)

Another very important tool for an electronic techlab is a function generator. The one that i am preparing to use is based on the MAXIM MAX038. This chip is rather expensive, yet has many capabilities. It can provide 3 different types of waveforms, triangular, rectangular and sine wave, as well as it provides a TTL output with 50% duty cycle for synchronization reasons. The frequency can be adjusted from 0.1 Hz up to 20 MHz.




The circuit

The circuit is based on the circuit provided by Maxim. I've done some modifications of course to fit my needs. This is the schematic diagram:







The above circuit covers some of the most important features that a function generator should have. The frequency range can be selected by placing a different capacitor to the COSC input. A 12 positions rotary switch with 12 different capacitors is perfect for this reason. The output frequency can be selected from within the frequency range, by changing the R7 potentiometer. The R6 potentiometer is the fine adjustment for the frequency.

The DADJ input of the chip is the control for the duty cycle of the waveform. I have a switch to either disable it (50% fixed duty cycle), or enable the duty cycle adjustment. If enabled, the duty cycle can be adjusted by the R8 potentiometer.

The output waveform type can be selected from the "FUNCTION" switch. This is a 3-position rotary switch. The common of the switch is driven HIGH, while the two inputs of the chip, A0 and A1 are pulled LOW with 10K resistors. When both inputs are '0', the output is square wave. When A0 is '1', the output is triangular waveform, and when A1 is '1' and A0 is '0', the output is sine wave.

The output is buffered with an OP37Z OP-AMP. The peak to peak amplitude is controlled by the potentiometer R5. By default, the output waveform is symmetrical to the ground. A DC offset can be added to the output if the switch "OFFSET ENABLED" is closed. The DC offset can be controlled by the R22.





















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  • At 6 May 2014, 7:38:24 user Giorgos Lazaridis wrote:   [reply @ Giorgos Lazaridis]
    • @weldor Well, not exactly. It can produce a waveform, but the problem for a tig welder is the driver rather than the frequency generator.


  • At 9 April 2014, 21:25:55 user weldor wrote:   [reply @ weldor]
    • This is my frst time here so please bear with me.
      Is there a way to adapt this circuit device to function as a part of a tig welder? I had electronics in high school the late 70's and am terribly rusty. I am now more of a gear head and would like to combine the best of two worlds.


  • At 19 January 2012, 4:22:18 user Marc Bonnier wrote:   [reply @ Marc Bonnier]
    • @Kammenos

      Ah, too bad. I will redo it from scratch then! Thanks for the quick answer :)


  • At 18 January 2012, 18:18:25 user Kammenos wrote:   [reply @ Kammenos]
    • @Marc Bonnier i discourage you to use this PCB because it causes a lot of interferences above some MHz. I am not sure if i have any of these PCB files any more (i had a fatal crash some time ago and lost almost all my older project files)


  • At 18 January 2012, 16:30:39 user Marc Bonnier wrote:   [reply @ Marc Bonnier]
    • Hi, like the user call Stefan, I have trouble printing out the PCB. You said it is 1:1 ration but the png is 1600x1606px which is way to big! Any 1:1 printing give more than a full page in size.


  • At 1 December 2011, 18:02:57 user sakthivel wrote:   [reply @ sakthivel]
    • i want 3hz to 3mhz with lcd frequency counter function generator circuits


  • At 24 July 2011, 7:01:51 user Kammenos wrote:   [reply @ Kammenos]
    • @Stefan the drawings are 1:1 dimensions. You can use them to print 1:1. I do not have the dimensions for them.


  • At 22 July 2011, 20:12:54 user Stefan wrote:   [reply @ Stefan]
    • What is the dimensions of the mask?I made the electronics but I can't get the messurments of the mask,please send me like a PDF file,or file you have made the mask.Thanks


  • At 5 June 2011, 13:41:16 user Kammenos wrote:   [reply @ Kammenos]
    • @Reishin check futurlec.com


  • At 2 June 2011, 21:25:23 user Reishin wrote:   [reply @ Reishin]
    • Hi Giorgos,

      I have a MAX038 chip and I'm planning to make the function generator detailed here. However, I'm having trouble locating the OP37Z op-amp. Do you know where I may be able to find one or can you recommend a replacement?

      Thanks


  • At 28 March 2011, 4:54:56 user Kammenos wrote:   [reply @ Kammenos]
    • @Lefteris Kosmas not exactly, 555 could not have that stability nor can it itself produce triangle and sine wave. It is indeed a must-have for all electronic workbenches.


  • At 27 March 2011, 21:15:19 user Lefteris Kosmas wrote:   [reply @ Lefteris Kosmas]
    • This is a lifesaver for DIY electronics labs. Well with a few mods you can use something like 555 IC for that baby or not?


  • At 14 March 2011, 16:50:48 user Kammenos wrote:   [reply @ Kammenos]
    • Hello Jogie. The chip is not produced any more, and is very expensive. I discourage you to copy this circuit. I did this because i had this in stock a lot time ago. If you find it somewhere in stock, it will cost a lot of money. I do not know a replacement part, and i do not think that exists one. But i do know that there are other chips with the same functionality.


  • At 14 March 2011, 14:17:47 user Jogie-ann Cabrillos wrote:   [reply @ Jogie-ann Cabrillos]
    • Hi Sir;

      Thanks for this site. I now found a fully working function generator, but sir, the chip which u use there is not available in Philippines. Can u recommend another IC to be used that is compatible with your circuit diagram. A replacement for the expensive IC sir coz i cant afford it, our school requires us to make function generator..

      Can u send me sir the schematic diagram with their respective components???

      Thanks Sir;
      jogie


  • At 16 February 2011, 18:01:18 user Kammenos wrote:   [reply @ Kammenos]
    • but i really do not suggest someone to buy this chip. there are cheaper around, and sure they have a datasheet with typical application schematic.


  • At 16 February 2011, 16:05:16 user Rick wrote:   [reply @ Rick]
    • The Max038 is still available at Futurlec for $22.90 usd.

      Rick


  • At 5 February 2011, 8:12:14 user Kammenos wrote:   [reply @ Kammenos]
    • Yes zzv, unfortunately you are right. I had this IC in stock many years ago.


  • At 4 February 2011, 21:21:33 user zzv wrote:   [reply @ zzv]
    • The only problem with this project is the chip availability and price. The MAX038 was discontinued by Maxim years ago and one can find it only overpriced on Ebay. Unfortunately there are no direct substitutes and no other chips that go up to 20 MHz as the MAX038 did. The only similar chips around are the XR2206 and the ICL8038 (which has absolutely nothing in common with the MAX038 despite the somewhat similar numeration), both are 20+ years old and both won't go much further one or two MHz.
      Nowadays if you want to build a modern signal generator DDS is the solution. Unfortunately it requires an additional MCU, more components and writing code.


  • At 20 November 2010, 6:32:39 user Ganesh wrote:   [reply @ Ganesh]
    • I want to 1HZ to 3 MHZ Function generator with display circuit


  • At 29 June 2010, 20:35:15 user Antonio Merenda wrote:   [reply @ Antonio Merenda]
    • Hi,
      I am Anthony Merenda radioamatore with it initials I8CQ, and I am enrolled to grix site Italian web, of electronic amatoriale. And having an integrated maxim 038, I have looked for on the web to find a project and the motor of search google you/he/she has brought me on his/her sito.Visto the project and his/her validity, I ask her if it authorizes me to pubbbicarlo on site web of grix.it. naturally you/he/she will be quoted both his/her site and the planner. aspect his/her news thanks.
      antonio snack I8CQ.
      P.S. I want to complimenti


  • At 21 April 2010, 20:48:08 user Kammenos wrote:   [reply @ Kammenos]
    • Hello Ivan,
      Most of my images, just like all schematics, can be enlarged when you click on them! Just click on the schematic.


  • At 21 April 2010, 20:44:50 user Ivan wrote:   [reply @ Ivan]
    • Hi Giorgos

      Thanks for this project. I really want to build one myself.
      Will it be possible for you to email me the circuit schematics in PDF format. The ones in the pages are too small to see it clearly.

      Thanks again.
      Regards
      Ivan





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