Oscillator question

[mettula]

Hello all, I need some help with this question

Which of the following statements is not true and why?

a. An oscillator must have a source of energy.
b. An oscillator must have a frequency determining circuit.
c. An oscillator must have an amplifier.
d. An oscillator must have a negative feedback circuit.

Is it b the one which is not right?
thanks a lot

[walid]

Hi

The statements which is not true is:

d. An oscillator must have a negative feedback circuit.

because  An oscillator must have a positive feedback circuit to maintain oscillation.
negative feedback is good for amplifiers to get more stability.

[mettula]

and yet another question which i cannot make my mind about.
what circuit produces a sine, square, triangular, and saw tooth waveforms
opamps or oscillators?
i mean oscillators can be build from opamps. what is the best answer to that

thanks

[walid]

I am not expert like Mr. guru, I will try to answer using my simple information :
Oscillators can be built using opamps or transistors or may be some special IC's.
opamps can not handle high frequency but transistors can
if u want to build a function generator try to search one in google or tell me to find one for u
That is all I know regarding your question, and I hope that others help me in the answer
Do not hesitate to ask about everything that comes to you

[audioguru]

Hi Walid,
I mentioned the obsolete ICL8038 and XR2206 function generator ICs in my reply to his PM.

[walid]

Thank you guru

[mettula]

Thanks guys.