# Miscellaneous

 Question 1
Consider the OP AMP based circuit shown in the figure. Ignore the conduction drops of diodes $D_{1}$ and $D_{2}$. All the components are ideal and the breakdown voltage of the Zener is $5 \mathrm{~V}$. Which of the following statements is true?

 A The maximum and minimum values of the output voltage $\mathrm{V}_{0}$ are $+15 \mathrm{~V}$ and $-10 \mathrm{~V}$, respectively. B The maximum and minimum values of the output voltage $\mathrm{V}_{0}$ are $+5 \mathrm{~V}$ and $-15 \mathrm{~V}$, respectively. C The maximum and minimum values of the output voltage $\mathrm{V}_{0}$ are $+10 \mathrm{~V}$ and $-5 \mathrm{~V}$, respectively. D The maximum and minimum values of the output voltage $\mathrm{V}_{0}$ are $+5 \mathrm{~V}$ and -10V, respectively
GATE EE 2023   Analog Electronics
Question 1 Explanation:
During positive hall cycle:
$\therefore \mathrm{D}_{1} \rightarrow \mathrm{ON}$ and $\mathrm{D}_{2} \rightarrow \mathrm{OFF}$
Redraw the circuit :

$\therefore V_0=-V_i$
$\quad (V_0)_{min}=-10V$
During negative half cycle :
$\mathrm{V}^{+} \gt \mathrm{V}^{-}$
Zener diode $\rightarrow$ ON, $\mathrm{D}_{1} \rightarrow$ OFF and $\mathrm{D}_{2} \rightarrow \mathrm{ON}$

Redraw the circuit:

$\therefore \quad (V_0)_{max}=5V$
 Question 2
Two monoshot multivibrators, one positive edge triggered $(M_{1})$ and another negative edge triggered $(M_{2})$, are connected as shown in figure

The monoshots $(M_{1})$ and $(M_{2})$ when triggered produce pulses of width $(T_{1})$ and $(T_{2})$ respectively, where $(T_{1} \gt T_2)$ . The steady state output voltage $(v_{o})$ of the circuit is
 A A B B C C D D
GATE EE 2014-SET-3   Analog Electronics
Question 2 Explanation:
Not in the GATE-2018 Syllabus.

 Question 3
The following circuit has a source voltage $V_s$ as shown in the graph. The current through the circuit is also shown.
The element connected between a and b could be
 A A B B C C D D
GATE EE 2009   Analog Electronics
Question 3 Explanation:
Diode act as a switch. When forward biased it is short circuited. But when suddenly reverse biased, current does not become zero instantly , initially the same current flow in opposite direction and after some time (turn off time) it will become zero.
 Question 4
The truth table of monoshot shown in the figure is given in the table below :

Two monoshots, one positive edge triggered and other negative edge triggered, are connected shown in the figure, The pulse widths of the two monoshot outputs $Q_1 \; and \; Q_2$ are $T_{ON1}$ and $T_{ON2}$ respectively.

The frequency and the duty cycle of the signal at $Q_1$ will respectively be
 A $f=\frac{1}{T_{ON_{1}}+T_{ON_{2}}},D=\frac{T_{ON_{1}}}{T_{ON_{1}}+T_{ON_{2}}}$ B $f=\frac{1}{T_{ON_{1}}+T_{ON_{2}}},D=\frac{T_{ON_{2}}}{T_{ON_{1}}+T_{ON_{2}}}$ C $f=\frac{1}{T_{ON_{1}}},D=\frac{T_{ON_{1}}}{T_{ON_{1}}+T_{ON_{2}}}$ D $f=\frac{1}{T_{ON_{2}}},D=\frac{T_{ON_{1}}}{T_{ON_{1}}+T_{ON_{2}}}$
GATE EE 2008   Analog Electronics
Question 4 Explanation:
$f=\frac{1}{T_{ON1}+T_{ON2}},$ $D=\frac{T_{ON1}}{T_{ON1}+T_{ON2}}$
 Question 5
IC 555 in the adjacent figure is configured as an astable multi-vibrator. It is enabled to to oscillate at t=0 by applying a high input to pin 4.
The pin description is :
1 and 8-supply;
2-trigger;
4-reset;
6-threshold
7-discharge.
The waveform appearing across the capacitor starting from t=0, as observed on a storage CRO is

 A A B B C C D D
GATE EE 2007   Analog Electronics
Question 5 Explanation:
An astable multi-vibrator is providing pulse as given below

But in this case initial voltage at capacitor is zero. So it starts from zero. Also charging time will be larger (normally) than discharging time but it is made equal by using a diode.

There are 5 questions to complete.