Hey Guys,
I've just started using easy eda. Which seems to be a great web app. I'll start by saying I'm relatively new to schematic/spice pcb apps as well as electronics in general so I apologize in advance!
I've got an issue with simulation which I was hoping someone might be kind enough to offer some advice or look at schematic and tell me where I've gone wrong. I'm sure there is probably a simple (embarrassingly so) problem to fix.
But I've tired working it out with no luck.
The schematic I'm trying to built is a RIAA phono inverting op amp based on the phonocube. I've built it on a breadboard (albeit with different op amp I think it was opa2134) and it worked fine.
Here is links hopefuly I've shared it correctly?
https://easyeda.com/editor#id=ab054771c95447e8b56925dc7ed7b079
https://easyeda.com/editor#id=ab054771c95447e8b56925dc7ed7b079
https://easyeda.com/normal/Zero_Impedance_Phono-ab054771c95447e8b56925dc7ed7b079
I've got a couple of issues/questions.
- I'm trying to simulate the frequency response based off a 1v/1k sine. The simulation based of selecting octave 100 increments 20hz to 20k runs fine without error but the graph FR results don't make sense? If I place a probe before op amp and RIAA curve I get a flat response which is as expected but when I put a probe after the 3.3uf output cap which is post RIAA compensation it seems I'm getting a result the exact opposite of what I'm expecting. Given that the RIAA pre emphasis sees a 20db cut at low end, 0db at 1khz and boost in high end I would expect that the response based of 1khz generator would see the bass 20+db 0 at 1khz and cuts to the highs, but this isn't the case. The FR response is cut in low end and boosted in highs. Does this make sense?
I'm not sure what I'm missing here or what I've done wrong but it ain't what I expected to see.
Any advice would be appreciated.
- The simulation seems to be running ok but I'm not sure if I have connected/setup dual rail power supply corrrectly?
And lastly.
I've had a look at details on the different type of simulations you can run but I can't work out what test and parameters I need to use to test gain of circuit? I want to provide a 0.4mv signal and test voltage at output. What test/parameters should I use?
Any help would be greatly appreciated, I'm new to electronics so my apologies again if I've asked some dumb questions!!!
Thanks heaps guys! I would really appreciate some help.
Hi Hyperterminal,
Welcome to EasyEDA.
I can see some of the things that are fouling up your simulation.
Most of them are understandable mistakes for a beginner so no problem.
:)
In any tool, simulation is not easy to get the hang of. It's just that some are easier than others!
So first off we strongly recommend that you work your way through the EasyEDA Simulation eBook:
https://docs.google.com/document/u/1/d/1OWZVVFRAe_2NW3WratpkA_SGuHa5AcRow5ZRfvcoVTU/pub
(The copy on the EasyEDA tutorials pages still has some problems with the Table of Contents and we have been too busy with the October upgrade to fix it.)
Next have a look at:
https://easyeda.com/forum/topic/How_to_find_simulatable_parts_in_EasyEDA-1YgasK2kC
Once you've done that you'll better understand the following description of why your sim isn't working as expected.
SHIFT+F
search forOP27_AD
you will find a symbol with a suitable model. Note that the offset pins of the OP27/OP37 devices are not modelled. If you need other variants of the OP27/OP37, please post back.In this last point, you can either feed a current in to the inverting input (also referred to as a virtual earth point) or you can add a series resistor to convert an input voltage into a current.
https://en.wikipedia.org/wiki/Operational_amplifier
https://easyeda.com/andyfierman/How_an_ideal_opamp_behaves_-43d981935602431abdb02faadf6b2ce1
and playing with it to get an idea of how opamps behave.
:)
If you fix points (1), (4) and (5), your circuit will simulate just fine.