# Waveform Generator Circuit Help

#### Remix23

Joined Mar 11, 2016
23
Hello,
I have a waveform generator circuit to analyze. Below is the circuit.

Reducing RL to 1k, 100 ohms. What do we observe.
Reducing RL, well there is no change in the waveform until it is dropped to 56 Ohms.

What is the reason why there is no change and what do we really see. I only see the scaling reduce.

Any ideas/support would be highly appreciated.

Last edited:

#### Remix23

Joined Mar 11, 2016
23
Okay, so what ive gathered is the capacitor cannot charge at 1000k, i see a flat line. but reducing it to 3.3k i see a triangular waveform. This allows the capacitor to charge.

Stuck with RL though

#### Remix23

Joined Mar 11, 2016
23
bump

#### MisterBill2

Joined Jan 23, 2018
8,761
Given that we have no information about the op amps or the power supply capability there is no predicting what will happen as the value of load resistor Rl is lowered. And given that the voltage at the non-inverting input of op-amp 3 is held at 4.5 volts, it will snap from positive to negative as the inverting input voltage varies above and below 4.5 volts. That is, unless it is an opamp with internal feedback.
THIS LOOKS A LOT LIKE HOMEWORK! and people paying for a classroom education should be listening and studying and not asking us for answers to their test questions.

#### Remix23

Joined Mar 11, 2016
23
Given that we have no information about the op amps or the power supply capability there is no predicting what will happen as the value of load resistor Rl is lowered. And given that the voltage at the non-inverting input of op-amp 3 is held at 4.5 volts, it will snap from positive to negative as the inverting input voltage varies above and below 4.5 volts. That is, unless it is an opamp with internal feedback.
THIS LOOKS A LOT LIKE HOMEWORK! and people paying for a classroom education should be listening and studying and not asking us for answers to their test questions.
For your information this is NOT HOMEWORK !!. this is a design i found online with questions to better myself with circuits.

#### MisterBill2

Joined Jan 23, 2018
8,761
For your information this is NOT HOMEWORK !!. this is a design i found online with questions to better myself with circuits.
OK, I am corrected in my presumption. But this IS the time of year when those who need help as final exams approach start asking for help. And quite probably it could have been a question for somebody bbefore it was posted where you saw it. It is a good trick question.

#### Remix23

Joined Mar 11, 2016
23
So we are only allowed to post questions in the month of july and august cause you'll assume its homework?

#### MisterBill2

Joined Jan 23, 2018
8,761
So we are only allowed to post questions in the month of july and august cause you'll assume its homework?
NO, that is not the case. And you can see that I did provide an answer. There is another current thread nearby where the TS has admitted that it is a big asignement and he had not been paying attention at all. So you just happened to catchsome of the grief by standing nearby. Sorry about that.

#### TeeKay6

Joined Apr 20, 2019
572
So we are only allowed to post questions in the month of july and august cause you'll assume its homework?
If you take the wrong attitude, it won't matter in which month you post, your question won't be answered. Your post certainly has the earmarks of a homework question. @MisterBill2 gave you a reasonable apology. Show your dignity and accept the apology. Growing a thick skin helps when conversing online; I have learned from experience. Then provide the missing information that MrBill2 highlighted, so that readers can help you. Learning is admirable, although often difficult, and everyone in this forum wishes you well in that respect.

#### Audioguru again

Joined Oct 21, 2019
3,188
Why don't your opamps have a part number?
The part number will link to its datasheet then its open-loop gain and maximum output current.

#### Remix23

Joined Mar 11, 2016
23
If you take the wrong attitude, it won't matter in which month you post, your question won't be answered. Your post certainly has the earmarks of a homework question. @MisterBill2 gave you a reasonable apology. Show your dignity and accept the apology. Growing a thick skin helps when conversing online; I have learned from experience. Then provide the missing information that MrBill2 highlighted, so that readers can help you. Learning is admirable, although often difficult, and everyone in this forum wishes you well in that respect.
He implied his question was prompted as exams are close. I haven't got to the apology yet and it's no biggy.

I hope on the next thread you're able to come across with open arms rather than a pistol.

I'm feeding 9 volts into the circuit. I have to change r5 down to around 3.3k otherwise I have a flat waveform. Second op amp shows a triangular and third square wave.

OP amp in use is an LM324