Electronics - Operational Amplifiers - Discussion

Discussion Forum : Operational Amplifiers - General Questions (Q.No. 29)
29.
What is the frequency of this 555 astable multivibrator?

mcq15_1038_1.gif
278 Hz
178 Hz
78 Hz
8 Hz
Answer: Option
Explanation:
No answer description is available. Let's discuss.
Discussion:
11 comments Page 1 of 2.

Murugan said:   7 years ago
T(high) = 0.693(RA+RB)C.
T(low) = 0.693(RB)C,
T = T(high)+T(low),
F = 1/T.
F = 1.44/(RA+2RB)C.
(2)

Madhur said:   1 decade ago
Its coming around 241HZ.
(1)

Sunny said:   1 decade ago
@vid

Explanation which you had given is wrong.

For Astable multivibrator, f=(1/T)= 1/(charg. time + discharging time)

or, f = 1/[0.69(Ra+2Rb)c].
(1)

Rakesh singh said:   1 decade ago
F = 1.44/(R1 + 2 R2)C

Buvana said:   1 decade ago
How is it can be correct? It is obscure for me.

Karuppasamy kpk said:   1 decade ago
According to the formula,

F= 1.44/((1000+2*6000000)10`9)

F=240.50 hz
Therefore,no one option is correct.

how can u say option B correct...?

Vid said:   1 decade ago
For astable t=1.4rc
f=1/(1.4(ra+2rB)c

Then i am getting 119.0

Kelly Jones said:   1 decade ago
f= 1.4427/[R1+(2*R2)]*C.
f= 1.4427/[1k+(2*3M)]*1.0 nano.
f= 1.4427/(1k+6M)*1.0 nano.
f= 1.4427/6.001M*1.0 nano.
f= 1.4427/6.001 milli.
f= 240.41 Hz.

Abbasi said:   10 years ago
For free running multivibrator.

f = 1.44/(R1+2R2)C.

Hence f = 239.96 Hz.

Sanjoy said:   10 years ago
Ton = (RA+RB) C1 = 3 ms.

Toff = RB*C1 = 3 ms.

T = Ton+Toff = 6 ms.

F = 1/T = 1/6 ms = 167 HZ.


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