how to increase slew rate of op-amp

thx!

which opamp you are using.

read this short pdf. u could get some idea... it depends on the compensating capacitor used.

/http://www.icaen.uiowa.edu/~bme080/lecture_notes/SlewRateNotes.pdf

/cedance

wany said:

thx!

Click to expand...

What causes SR? actually there is usually a capacitor within or out side of the opamp to prevent oscillation. it is the capacitor which prevents the output voltage to respond immidiately to the input. So the SR can be defind as SR = Imax/C.
so if we want to increease the SR then we have to decrese the C. this is again depand on the manufacturer. so one way is to go for ultra fast opamp like LH0032. it is a noncompesated device and boasts a 500V/microsecond. with a 70Mhz bandwidth.

but when we are working with such fast device the circuit layout becomes far more critical than normal.
you may take some prevantion for good result
1. PC-board ground planes are advised.
2.shielding around the input and output path may lso be required for some application.
3. the circuit lay out should be designed to minize stray capacitance between the output and feedback point.
4. IC sockets are generally avoided to avoid the capacitance by these.


try this
byom

If you are talking in IC Design term

A typical formula for slew rate for a normal 2 stage opamp is SR= Icc/Cc

Icc is you tail current and Cc is the compensation capcitor.

So, to increase SR:
1. increase Icc, or
2. reduce Cc, or
3. both

1.increase curr
2.decrease load capacitance
3.work with small transistors
4.increase over drives

increase id1 ( this also increses ugb) or
decrease value of compensating capacitor , but this also increases the ugb(unity gain band width)

What do u mean by a compensation capacitor here? does the input capacitor fall into the caegory? because I am working with APEX pa107dp and it is such a fast ampr (slew rate of 3000V/us) but I don't find any change in SR by changing the input capacitance


Regards