My Circuit does not work in Simulation Mode. What have I done wrong?
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Maxi Steiner 2 months ago
Hey! This is my first project in EasyEDA. (also sorry for my bad english) I am making this as part of a Project for university. In this project I want to build a selfmade "Ladder Filter" with templates from Bob Moog. This is basically an array of transistors (hence the name "ladder") which functions as a 24dB/Octave Low Pass Filter with an integrated Feedback loop for self oscillation/ saturation. ![Ladder Filter Layout.png](//image.easyeda.com/pullimage/NNMLC3imdTi7gxs8VQwBD1AROn68sHyLYMf5b55x.png) Before building my circuit I tried to simulate it and built the schematics as you can see in the picture above. Every time I try to start the simulation, it shows an error with an "unknown subcurcuit called in". I`m quite desperate right now.. :D If someone could tell me what my mistakes are in this simulation, i would be very happy and greatful.
Comments
andyfierman 2 months ago
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.
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andyfierman 2 months ago
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.
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Markus_ee 2 months ago
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
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andyfierman 2 months ago
@maxisteiner57, Replace the opamps with TL071EE. Use two voltage sources to generate +/-8V. ![image.png](//image.easyeda.com/pullimage/KVVjSS4afx9SzeQdBmAvvbdnkTis5IceienZ6X6o.png) Sort out the connectivity at the input to your input stage. At the moment both inputs are shorted together: ![image.png](//image.easyeda.com/pullimage/Vy1zbS7ms0T6vFIwhxgh0Sa1dSnWs6lgR3x2DPOP.png) 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>
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Maxi Steiner 2 months ago
@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.
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andyfierman 2 months ago
@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.
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andyfierman 2 months ago
@maxisteiner57, BTW, this does not work because you have no dc path for the opamp input bias currents: ![image.png](//image.easyeda.com/pullimage/JA8pe5iFXBLr4F5CMz6pGHWQNcAHPZmLRBRXieL7.png)
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andyfierman 2 months ago
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/)
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