Hi all.

I am trying to build a PID controller using Op Amps. A second order plant has been designed using OP amps. I have simulated the whole closed loop system in PSPICE and the step response is satisfactory. The schematic is attached below.

Now my question is:
1. What Op Amps I should use to implement this circuit? LM741 or TLO84 or LM324? For getting a step response the 'V5' in only 1V.
2. What type of capacitors should I use? 1uF ceramic capacitors are not available, so should I use mylar or electrolytic ones? or should i use a 0.1 uF capacitor and change the variable resistances such that the gain remains constant?

Any help would be appreciated.

 

What keeps U7 from saturating? Maybe a very large resistor actoss C2 would help.

I would go with the TL084 over the
741 and 324.

You can use any unpolarized capacitor. X7R ceramic would be my first choice. Either that or scale up the impedances and resistances and use .01 uf NPO ceramics.

 

What keeps U7 from saturating? Maybe a very large resistor actoss C2 would help.

I would go with the TL084 over the
741 and 324.

You can use any unpolarized capacitor. X7R ceramic would be my first choice. Either that or scale up the impedances and resistances and use .01 uf NPO ceramics.

Thank you for your reply.

If I use .01uf NPO ceramic capacitors and scale the resistances up, will there be any unwanted distortion in the output? What is the highest value of resistance you can use in the feedback path?

 

What is the highest value of resistance you can use in the feedback path?

I would keep it below 5 million ohms with a TL08x series chip.

 

What keeps U7 from saturating? ..................

The closed loop DC feedback should do that, at least in steady-state.

 

What Op Amps I should use to implement this circuit? LM741 or TLO84 or LM324?

assuming dual-rail power supplies, and the component values specified, pretty much any of them will do.