# How many times is the signal amplified before oscillation?

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#### brahma

oscillators

when positive feedback is applied to opamp it will starts oscillate at a particular frequency giving out a single frequency. i want to know how many number of times the signal is feed back and amplified before we get a sustained oscillation???

#### Davood Amerion

Re: oscillators

how many number of times the signal is feed back and amplified before we get a sustained oscillation?
I think this is continues for ever.

#### v_c

Re: oscillators

I think you are talking about startup time here - in other words, how long do you have to wait until you have sustained oscillations with constant amplitude.

I don't know if you can calculate this generically without having a oscillator circuit. Most of the time, the oscillator startup is given on a datasheet -- for example, in crystal-based oscillator circuits. You could also simulate if you have the proper models.

Look at the bottom of page 3 of this datasheet. The manufacturer is claiming a startup time of around 1ms.

Best regards,
v_c

##### Full Member level 3
oscillators

The time required to start oscilation is dependant on the resonant frequency of the circuit and the amount of feedback and can vary quiet a bit.

#### chegu.balaji

##### Junior Member level 1
oscillators

pls can anyone help me how to calculate the startup time of an oscillator.for example a WEIN BRIDGE oscillator using an opamps & R,C elements

#### brahma

Re: oscillators

ok even if we know the startup time how to get 'how many of times it is feeded back and amplified???

#### bjeservice

##### Member level 2
oscillators

Dear friend
i think there is misunderstood of the phenomena.
1-first you got the output frequency because there is a noise output signal ( filterd ) by the feed back loop of the oscillator ( which specify the frequency )
2-the sustained is for amplitude not frequency of the signal
3. the oscillation frequency is the only sustained signal in oscillator the other frequencies are damped

so i think the signal exist fom the start of operation of op amp after the Vcc voltage bring the op amp to work, but the amplitude will take several loop to reach its final value

practically may a storage scope help you to find the time you want to reach required level of output frequeny ,you start the scope first then record the signal and you will see the time that it will reach level

theoritacly it is so difficult to simulate the situation becuse the starting depends on other factors like the non linearity of amp. , stray components effects ......

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