This thread has been locked.
If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.
Part Number: LM741
To hom it may concern
I'm using two LM741 to make a triangle signal, but the signal is umbalanced respect zero. Positive part is 1.8 V and negative part is 2.8 V in the output of the first ampop and simmilar to the output of the second. I rode about 1,5 pins offset balance, but as I understand it is just to balance feeding. I'm using a PC's power supply where I get 12 V and -11.5 V. The feeding balance is opposite of what I'm getting. What do you suggest to do to get a balanced output (simmilar positive and negative parts of the signal) respect zero?
Thank you for your valuable time
In reply to kai klaas69:
I noted the feedback trough a 47 K resistance. I'll make some tests. So to shift down output I'd need to feed V5 with a lower than zero voltaje? Would it work to shift it in the original circuit?
We are glad that we were able to resolve this issue, and will now proceed to close this thread.
If you have further questions related to this thread, you may click "Ask a related question" below. The newly created question will be automatically linked to this question.
In reply to user5866636:
in my last simulation I have set V5=1V. This shifts up the triangle wave. A negative V5 would shift it down:
Please notice that I have taken a supply voltage of +/-12V. When using an unbalanced supply voltage you might need V5 to recover the balance of output signal, like shown in this example:
But I would not use an unbalanced supply voltage, because this will make the triangle become asymmetrical, as shown in this example:
It's best to have a well regulated and stable bipolar supply voltage which is balanced. Take care, PC supply voltages can be very noisy and full of ripple. I wouldn't use them for this circuit.
In your original circuit the triangle wave is unbalanced because the LM741 shows different slew rates for the rise and the fall of output voltage. The LM741 is totally overstrained in this circuit and will not show a stable performance. Slew rates depend on several factors like temperature, etc. . So, you might need to adjust the shifting all the time when using this circuit. And the frequency will not be stable either. I wouldn't use your original circuit.
Thank you very much for your advices, I'll make some tests.
I'd like to know which are the 'overstrain' conditions in a lm741.
by "overstrained" I mean that the LM741 is much too slow for this circuit. Have a look at your original circuit again: U6 is actually meant as a square wave oscillator. With a proper chosen OPAmp, which is fast enough, the output signal of U6 would look like this:
You can see that the output signal is a square wave. But now see what the LM741 is doing in the same circuit:
The edges are so slow that the output signal looks like a triangle wave and not a square wave as it should. So, the LM741 is much much too slow for this circuit.
For such a square wave oscillator an OPAmp with a high slew rate must be chosen. The LM741 has a slew rate of 0.5V/µs. But the TL082 has a slew rate of 13V/µs. So, the TL082 is 26 times faster!
In reply to Daniel Miller56:
It says that my account (new) is not ellegible for samples, and if I want to know why to do click in a link, which is not available.
If you know what are the requisites for it, I'll consider TI components for the design. Indeed, I have a provider in China for printed circuit boards, I'd like them to build the complete circuit, but I suppose then you would provide them. Have you a dealer in China?
All content and materials on this site are provided "as is". TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with regard to these materials, including but not limited to all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement of any third party intellectual property right. No license, either express or implied, by estoppel or otherwise, is granted by TI. Use of the information on this site may require a license from a third party, or a license from TI.
TI is a global semiconductor design and manufacturing company. Innovate with 100,000+ analog ICs andembedded processors, along with software, tools and the industry’s largest sales/support staff.