Multivibrators and 555 Timer

Question 1
In the astable multivibrator circuit shown in the figure, the frequency of oscillation (in kHz) at the output pin 3 is __________
A
2.50
B
6.55
C
5.68
D
1.55
GATE EC 2016-SET-3   Analog Circuits
Question 1 Explanation: 
\begin{array}{c} f=\frac{1}{0.69\left(R_{A}+2 R_{B}\right) C} \\ =\frac{1}{0.69\left(2.2 \times 10^{3}+2 \times 4.7 \times 10^{3}\right) \times 0.022 \times 10^{-6}} \\ =5.6818 \mathrm{kHz} \end{array}
Question 2
In the following a stable multivibrator circuit, which properties of v_{0}(t) depend on R_2?
A
Only the frequency
B
Only the amplitude
C
Both the amplitude and the frequency
D
Neither the amplitude nor the frequency
GATE EC 2009   Analog Circuits
Question 3
Consider the Schmidt trigger circuit shown below. A triangular wave which goes from -12 to 12 V is applied to the inverting input of OPMAP. Assume that the output of the OPAMP swings from +15 V to -15 V. The voltage at the non-inverting input switches between
A
-12V to +12 V
B
-7.5 V to 7.5 V
C
-5 V to +5 V
D
0 V and 5 V
GATE EC 2008   Analog Circuits
Question 3 Explanation: 
\begin{aligned} \frac{15-V_{1}}{10}+\frac{V_{0}-V_{1}}{10}&=\frac{V_{1}-(-15)}{10} \\ 15-V_{1}+V_{0}-V_{1}&=V_{1}+15 \\ \Rightarrow \quad V_{1}&=\frac{V_{0}}{3} \end{aligned}
since, V_{0} swings from -15 \vee to +15 V,
Therefore, V_{1} switches between -5 \vee \text{ and } +5 \mathrm{V}
Question 4
An astable multivibrator circuit using IC 555 timer is shown below. Assume that the circuit is oscillating steadily.

The voltage V_c across the capacitor varies between
A
3 V to 5 V
B
3 V to 6 V
C
3.6 V to 6 V
D
3.6 V to 5 V
GATE EC 2008   Analog Circuits
Question 4 Explanation: 
V_{C} varies between 3V to 5V.
Question 5
Given the ideal operational amplifier circuit shown in the figure indicate the correct transfer characteristics assuming ideal diodes with zero cut-in voltage.

A
A
B
B
C
C
D
D
GATE EC 2005   Analog Circuits
Question 5 Explanation: 
V_{u t}=\beta_{u} V_{\text {sat }}
When lower diode is ON
\begin{aligned} \beta_{u}&=\frac{2 k \Omega}{2.5 \mathrm{k} \Omega} \\ \therefore \quad V_{u t}&=\frac{2}{2.5} \times 10=8 \mathrm{V} \\ V_{l t}&=-\beta_{l} V_{s a t} \end{aligned}
(when upper diode is ON, \beta_{l}=\frac{2 \mathrm{k} \Omega}{4 \mathrm{k} \Omega}=\frac{1}{2})
=-\frac{1}{2} \times 10=-5 \mathrm{V}
V_{u t} \& V_{l t} are upper and lower transition voltage.
Question 6
Consider the following two statements:

Statement 1: A stable multi-vibrator can be used for generating square wave.
Statement 2: B stable multi-vibrator can be used for storing binary information.
A
Only statement 1 is correct
B
Only statement 2 is correct
C
Both the statements 1 and 2 are correct
D
Both the statements 1 and 2 are incorrect
GATE EC 2001   Analog Circuits
There are 6 questions to complete.
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