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I am constructing 10kHz , 30kHz and 50kHz sine waves using wien bridge oscillator design with LM358 OP-Amp. I have a few problems with the circuits that i could not figure out. Thank you for all your helps.

1)The output sine waves are getting distorted as the frequency increases. It is OK for 10kHz but when i increase the frequency more to 30kHz or to 50kHz I am getting the following distortions on my waves. I have tried changing the Op-Amp, (not the model), changing the source changing the values for resistors but could not fix it. Distortions at 30kHz

2) And secondly I want to amplify the waves but non-inverting amplifier or inverting amplifier with only resistors aren't working. I've read the data sheet of LM-358 there is an example amplifier circuit for AC signals. However I couldn't figure out what component does what. Do I have to use that circuit or is there a simpler solution. Example Amplifier Circuit

Again Thank you for all your kind help.

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  • \$\begingroup\$ From the related questions, definitely try to implement this with ±V rails and use something like in electronics.stackexchange.com/questions/78388/… . Find an op-amp with enough GBW and slew rate to have a good output at the desired frequency, then you can have a much higher frequency ceiling. Be careful with very high GBW op-amps, though, they like to have uncontrolled oscillations. \$\endgroup\$
    – user2943160
    May 20, 2016 at 5:30
  • \$\begingroup\$ What wien bridge circuit did you use? \$\endgroup\$
    – Andy aka
    May 20, 2016 at 9:03
  • \$\begingroup\$ This one: i.stack.imgur.com/Idtcq.jpg \$\endgroup\$
    – Dhasvan
    May 20, 2016 at 12:16

1 Answer 1

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1) Sorry to be the bearer of bad tidings, but running a 358 at more than about 10 kHz is a losing proposition. The data sheet show figure 7 (page 10) shows maximum voltage swing vs frequency, and you can see that 10 kHz is marginal, and 30 kHz and 50 kHz are worse. Get a faster op amp.

2) You do need all those components, but there is also a "simpler" way to do it. Get a second power supply and drive your circuit with +/- voltage, and your circuits will be greatly simplified.

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  • \$\begingroup\$ Thank you for your response. Which Op-Amp do you suggest? For example do you think LM741 would be sufficent? I am using 2 supplies +12V and -12V. \$\endgroup\$
    – Dhasvan
    May 19, 2016 at 22:19
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    \$\begingroup\$ A 741 is even worse. Am I correct in thinking you need a DIP package? \$\endgroup\$
    – WhatRoughBeast
    May 19, 2016 at 23:02
  • \$\begingroup\$ Yes i need DIP package :) \$\endgroup\$
    – Dhasvan
    May 19, 2016 at 23:06
  • \$\begingroup\$ If you read here electronics.stackexchange.com/help/on-topic you'll see that shopping recommendations are not kosher here, but I'll give you some guidelines. Go to one of the on-line electronics distributors (Digikey, Mouser, Newark, Allied, etc) and call up a product selection page for op amps. You'll need to look for voltage supply 36 volts, gain-bandwidth product at least 3 MHz (and 10 times better won't hurt), and slew rate of 6-7 V/usec or better. And DIP package, of course. If you're really uncertain, come back with your best choice and open a question about its appropriateness. \$\endgroup\$
    – WhatRoughBeast
    May 20, 2016 at 0:59
  • \$\begingroup\$ An LF353 8 pin dip has a 13V/uS slew rate and a gain bandwidth product of 4 MHZ, but you will need a bipolar power supply of +/- 12 to +/- 15 volts. \$\endgroup\$
    – user105652
    May 20, 2016 at 0:59

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