TINA spice simulation gives floating warnings

[inkl]

ok, I added R5=47 Ohm and now I have the following:

gain:

so why is this R5 is so critical?


Well, I just started reading about op amps...

 

[audio_tony]

ok, I added R5=47 Ohm and now I have the following:
so why is this R5 is so critical?

Briefly;

R5 will isolate the opamp from a capacitive load, and prevent oscillation.

Here is a very detailed explanation.

 

[inkl]

I just found out that if I set the voltage back to 3,3V I get that weird gain curve again. And it stays the same no matter if there is R5 or not. But increasing VCC to 5V gets back things to normal...

 

[audio_tony]

I just found out that if I set the voltage back to 3,3V I get that weird gain curve again. And it stays the same no matter if there is R5 or not. But increasing VCC to 5V gets back things to normal...

That's because the supply voltage is too low for the required gain.

By the way, the LT1215 is not a good choice for your application, it looks to have a high noise figure.

Try using an NE5532 for your sims because once that works reliably you can then try alternate OPAMPS.

 

[inkl]

ok, I made another one, from Project 93:

But here's what I get in the diagram:

I don't get what it means? Also, I'm not sure I put that zener diode right. Can you please let me know what's wrong with it? The simulation seems to be correct...

 

[audio_tony]

Setup some test points around the circuit and do a DC simulation, take a screenshot and post it here.

It's highly unlikely this circuit will offer better performance and gain than an OPAMP though.

 

[jorgovanko]

I would like to ask here not to open another topic... I am trying to simulate the PeeCeeBee V4H amplifier ( https://www.diyaudio.com/community/threads/peeceebee-v4h-gb.317151/ ) in the TinaTI program. Everything is OK, except I can't get a square signal response. The circuit is attached. Everything else is OK, except for a slightly higher THD compared to the amp specifications.
I would ask for help. Thanks.