Your simulation fails because you are using symbols that have no spice models associated with them. Please read - and play with the examples  in - the **Simulation Tutorial**  before attempting to simulate your circuit.

The spice symbols you need to do this are all in the Spice Symbol library. You just need to understand where to look for them and why.

Hi! When you have successfully simulated your circuit, you do know what to do? Add decoupling capacitors to the voltage input pins of your operational amplifiers :-) Regards, Markus Virtanen HW / Electronics Designer

@maxisteiner57, Replace the opamps with TL071EE. Use two voltage sources to generate +/-8V.  Sort out the connectivity at the input to your input stage. At the moment both inputs are shorted together:  You can use the fancy scope, sig gen etc., or just use the basic voltage sources and probing techniques described in the Simulation Tutorial. See also: [https://easyeda.com/forum/topic/How-to-use-the-EasyEDA-Oscilloscope-759bdd4ce3604beab90df403dbc14b69](https://easyeda.com/forum/topic/How-to-use-the-EasyEDA-Oscilloscope-759bdd4ce3604beab90df403dbc14b69)<br> <br> and you might like: [https://easyeda\.com/andyfierman/Precision\_sawtooth\_to\_triangle\_wave\_converter\-eb9567312a3b431f9ce8062f170fe97f](https://easyeda.com/andyfierman/Precision_sawtooth_to_triangle_wave_converter-eb9567312a3b431f9ce8062f170fe97f)<br> <br> <br> <br>

@andyfierman thank you very much for your advice! Are the TL071EE fundamentally the same as the TL071 I use here? In my real world project I will use OP07 opamps and a assembled power supply delivering +16V /-16V. That is why I created my 16V voltage source.

@maxisteiner57, "Are the TL071EE fundamentally the same as the TL071 I use here?" Your question does not make sense because you are not using a TL071. You have placed a symbol for a TL071 but that symbol has no spice model associated with it. If you mean "Does the TL071EE in-house spice model simulate a real TL071 well enough to use in your simulation?" then the answer is yes. "In my real world project I will use OP07 opamps and a assembled power supply delivering +16V /-16V. That is why I created my 16V voltage source." The supply you have placed on your schematic is a single 16V source with no ground reference so it cannot represent a split +/-16V supply. I assume that you are keeping the project private because you are doing this as a college project.

@maxisteiner57, BTW, this does not work because you have no dc path for the opamp input bias currents: 

I knew I'd done one of these before: I just couldn't remember where it was. I did it in the days before Dillon came along and stole my soul... [https://www.circuitlab.com/circuit/5mpdus/moog-4th-order-lowpass-ladder-filter-01/](https://www.circuitlab.com/circuit/5mpdus/moog-4th-order-lowpass-ladder-filter-01/)