Hey All,

I have bread boarded a phase shift oscillator which worked for some time then it doesn't work. I tried the 741, 324, and 339 op amps. The feedback network consists of 1k and 56k. And the phase shift network consists of 0.1u capacitors and 100 resistors. I tried both 3 and 5 phases networks and it worked.

Each lasted about 3 minutes until I turned the power off (9 volts). Now it doesn't work. I don't know why?

Thanks.

 

post a schematic

 

http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/ietron/pso2.gif

The link is the same that I used. In correlation to the resistor numbers on the image, they are

R1 = 1k
R2 = 56k

Capacitors all are 0.1u
And the remaining resistors are 100 Ohm

 

The circuit wants a dual (+, - and ground) power supply. Are you using a single 9V supply?

 

The circuit wants a dual (+, - and ground) power supply. Are you using a single 9V supply?

Yes, I'm using one 9 volt battery. But I have two electrolytic capacitors between the positive and negative forming the ground.

 

It works for me in simulation with a generic op amp and a ±4.5V supply (5.88kHz). Try a large value resistance like a 10kΩ resistors in parallel with each of the electrolytics (resistive voltage divider).

 

±4.5V rails on those old opamps doesn't leave alot of room for the output swing.

 

Hey folks, thanks for the help. I found out what I did wrong. I had the resistors and capacitors backwards in the phase shift network.



So when I changed that and made the minor changes you suggested everything worked. I tried 3,5, and 7 phase with no problem.