need help in this schematic (function generator)

Audioguru

Joined Dec 20, 2007
11,249
It is not a function generator. It is a poor sine-wave generator.
It needs another opamp as a buffer so that the third RC network is not loaded down by the 7.5k and 20k resistors of the inverting amplifiers.

It does not have an amplitude limiting circuit so its output will be clipped.
 

Attachments

Wendy

Joined Mar 24, 2008
22,360
You seem to be on an endless quest for a function generator. This is about the 5th thread you've started for this (more?). Did the others we went over not work, or are you trying to understand oscillators?

There are chips that will do this, though they are a bit more complex in parts.
 

Thread Starter

endaya_walatch

Joined Sep 13, 2009
33
It is not a function generator. It is a poor sine-wave generator.
It needs another opamp as a buffer so that the third RC network is not loaded down by the 7.5k and 20k resistors of the inverting amplifiers.

It does not have an amplitude limiting circuit so its output will be clipped.
oh...thanks for the immediate reply.. by the way, i'm still curious about how to get the frequency in this circuit?? can you help me again?
 

Thread Starter

endaya_walatch

Joined Sep 13, 2009
33
You seem to be on an endless quest for a function generator. This is about the 5th thread you've started for this (more?). Did the others we went over not work, or are you trying to understand oscillators?

There are chips that will do this, though they are a bit more complex in parts.
yup.. i have a difficulty in understanding those schematic so i prefer to study one by one...
 

Wendy

Joined Mar 24, 2008
22,360
Wikipedia has a pretty good article on phase shift oscillators. Basically each RC leg shifts the target frequency 60°. Do this three times and you have 180°. Add an inverting amplifier for another 180° phase shift and you have positive feedback, which all oscillators need. The reason it is a sine wave oscillator is only one frequency will shift 60° in each RC leg, all other frequencies don't meet this mathimatical requirement.
 
Top