For the astable multivibrator shown in Fig. 7.1:
(a) Determine the time period and the frequency of oscillations if $\ R_{1} = R_{2} = R$ = 10 kΩ , $\ C_{1} = C_{2}$ = 0.01 μF.
(b) Determine the time period and the frequency of oscillations if $\ R_{1}$ = 1 kΩ, $\ R_{2}$ = 10 kΩ, $\ C_{1}$ = 0.01μF, $\ C_{2}$ = 1μF.

Question

For the astable multivibrator shown in Fig. 7.1:
(a) Determine the time period and the frequency of oscillations if[latex]\ R_{1} = R_{2} = R[/latex] = 10 kΩ ,[latex]\ C_{1} = C_{2}[/latex] = 0.01 μF.
(b) Determine the time period and the frequency of oscillations if[latex]\ R_{1}[/latex] = 1 kΩ,[latex]\ R_{2}[/latex] = 10 kΩ, [latex]\ C_{1}[/latex] = 0.01μF,[latex]\ C_{2}[/latex] = 1μF.

Accepted Answer

(a) Given[latex]\ R_{1} = R_{2} = R[/latex] = 10 kΩ,[latex]\ C_{1} = C_{2}[/latex] = 0.01 μF.
This is a symmetric astable multivibrator.

[latex]\ f = \frac{0.7}{RC} = \frac{0.7}{10 × 10^{3} × 0.01 × 10^{−6}}[/latex] = 7 kHz.

(b) Given[latex]\ R_{1}[/latex] = 1 kΩ,[latex]\ R_{2}[/latex] = 10 kΩ,[latex]\ C_{1}[/latex] = 0.01 μF,[latex]\ C_{2}[/latex] = 0.1 μF

This is an un-symmetric astable multivibrator:

[latex]\ T = 0.69(R_{1}C_{1} + R_{2}C_{2}) = 0.69(1 × 10^{3} × 0.01 × 10^{−6} + 10 × 10^{3} × 0.1 × 10^{−6})[/latex] = 0.69 ms

[latex]\ f = \frac{1}{T} = \frac{10^{3}}{0.69}[/latex] = 1.45 kHz

Chapter 7

Q. 7.3

Q. 7.3

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