bubba lm348

[flavius]

i was trying to make this bubba lm348 oscillator

can't make it work

can someone help me?

[Mahmoud_W]

Hi,

You needed to connect your unwired opamp terminals to ground and change your lower supply volt from 0 to -5V.

I attached back your modified file.

Mahmoud W

NI

[Phoenix_52]

Hi All,

I am currently working on a Oscilator to generate 60 Hz freq. With Single Supply and a voltage reference. 

I tried the following circuit in Multisim. But the circuit is not oscilating. Currently you will see two batteries used however the 6 volt battery will be later replaced by a voltage regulalor powered by the single 12v battery.

Can someone please help me out here.

Regards,

Mustafa

[Tien_P]

Hi Mustafa,

The opamp model you used is a three pin model where the power supply is not taken into consideration; I replaced the model with a TI model with five pin model. To replace a model, you can double click on the opamp then click the "Replace" button, in the "Model manufacturer/ID" area, you should see a few different opamp model for this part, you have to do this for each section. Have a look at this knowledge base for more information three terminal opamp model:

http://digital.ni.com/public.nsf/allkb/08A90AA832928553862570C100317437

To get the circuit to oscillate, I set the initial condition to zero from the menu Simulate»Interactive Simulation setting, click the down arrow in the "initial condition".  This setting will get the circuit to begin oscillating but after a short period, the signal will flat line.

Next, I increased R2 to 1.6M to increase the circuit gain and this seems to have stopped the circuit from flat lining.

[Phoenix_52]

Hi Tien,

Thanks a lot Tien for the help, really appreciate. That means in Real Life on the bread board we need to adjust the R2 resistor to make sure the signal does not become flat.

Thanks,

Mustafa

[Hassan14]

Can anyone please inform me that what mistake i have done in this oscillator due to which i get the wrong output response......

[Tien_P]

In general you should remove unused parts from the schematic.  Although they may not be connected to the circuit, the SPICE simulator sees them and they are included in the calculation.

U4A, the two inputs pins are connected in reversed.

For a single rail opamp connection, the DC connection to the input is usually half the positive rail, in the case you need to change the value from 12V to 6V, again this is connected to U4A.

[Hassan14]

Hi Mr Tien P 

Recently i was working on a project sinewave ups and bubba oscillator is one of the part of this project which i successfully achieved by your coordination Thank you very much....