GATE EC Op-amp Circuits questions

In the voltage reference circuit shown in the figure, the op-amp is ideal and the transistors $Q_1, Q_2, \dots ,Q_{32}$ are identical in all respects and have infinitely large values of common-emitter current gain $(\beta)$. The collector current $(Ic)$ of the transistors is related to their base-emitter voltage ($V_{BE}$) by the relation …

The following signal $V_i$ of peak voltage $8 \: V$ is applied to the non-inverting terminal of an ideal Op-amp.The transistor has $V_{EE}=0.7 \: V$, $\beta=100; \: V_{LED}=1.5 \: V$, $V_{CC}=10 \: V$ and $– V_{CC}= – 10 \:V$. The number of times the LED glows is ________

Consider the oscillator circuit shown in the figure. The function of the network (shown in dotted lines) consisting of the $100 \: k \Omega$ resistor in series with the two diodes connected back-to-back is to:

The block diagram of a frequency synthesizer consisting of a Phase Locked Loop (PLL) and a divide-by-$N$ counter (comprising $\div 2, \div 4, \div 8, \div 16$ outputs) is sketched below. The synthesizer is excited with a $5$ kHz signal (Input $1$). The free-running frequency of the PLL is set to $20$ kHz. Assume that the commutator switch makes …

The output of the combinational circuit given below is

A superheterodyne receiver operates in the frequency range of $58$ MHz – $68$ MHz. The intermediate frequency $f_{IF}$ and local oscillator frequency $f_{LO}$ are chosen such that $f_{IF} \leq f_{LO}$. It is required that the image frequencies fall outside the $58$ MHz – $68$ MHz band. The minimum required $f_{IF}$ (in MHz) is _________

A network consisting of a finite number of linear resistor (R), inductor (L), and capacitor (C) elements, connected all in series or all in parallel, is excited with a source of the form $$\sum_{k=1}^{3} a_k\cos(k\omega_0t) ,\text{where } \thinspace a_k\neq 0, \omega_0\neq0$$ The source has nonzero impedance. Which one of the following is a possible form of …

An ideal opamp has voltage sources $V_1, V_3, V_5, \dots, V_{N-1}$ connected to the non-inverting input and $V_2, V_4, V_6, \dots, V_N$ connected to the inverting input as shown in the figure below $(+V_{CC}= 15$ volt, $– V_{CC} = – 15$ volt). The voltages $V_1, V_2, V_3, V_4, V_5, V_6, \dots$ are $1, -1/2, 1/3, -1/4, 1/5, -1/6, \dots$ volt, …

The switch has been in position $1$ for a long time and abruptly changes to position $2$ at $t = 0$. If time $t$ is in seconds, the capacitor voltage $V_{C}$ (in volts) for $t > 0$ is given by

An opamp has a finite open loop voltage gain of $100$. Its input offset voltage $V_{ios}(=+5mV)$ is modeled as shown in the circuit below. The amplifier is ideal in all other respects. $V_{\text{input}}$ is $25 \: mV$. The output voltage (in millivolts) is _________

In the feedback system shown below $G\left ( s \right )=\frac{1}{\left ( s^{2}+2s \right )}$. The step response of the closed-loop system should have minimum settling time and have no overshoot. The required value of gain $k$ to achieve this is __________

In the feedback system shown below $G\left ( s \right )=\frac{1}{\left ( s+1 \right )\left (s+2 \right )\left ( s+3 \right )}.$ The positive value of $k$ for which the gain margin of the loop is exactly $0$ dB and the phase margin of the loop is exactly zero degree is _________

In the astable multivibrator circuit shown in the figure, the frequency of oscillation (in kHz) at the output pin $3$ is _______

For a superheterodyne receiver, the intermediate frequency is $15\ MHz$ and the local oscillator frequency is $3.5\ GHz$. If the frequency of the received signal is greater than the local oscillator frequency, then the image frequency (in $MHz$) is _______

In the circuit shown, assume that the opamp is ideal. The bridge output voltage $V_0$ (in mV) for $\delta=0.05$ is __________

The circuit shown in the figure has an ideal opamp. The oscillation frequency and the condition to sustain the oscillations, respectively, are

In the circuit shown, $V_{0} = V_{0A}$ for switch $SW$ in position $A$ and $V_{0} = V_{0B}$ for $SW$ in position $B$. Assume that the opamp is ideal. The value of $\dfrac{V_{0B}}{V_{0A}}$ is ___________.

In the bistable circuit shown, the ideal opamp has saturation levels of $\pm\: 5\: V.$ The value of $R_{1} \text{(in}\: k\Omega)$ that gives a hysteresis width of $500\: mV$ is ________.

Assuming that the opamp in the circuit shown below is ideal, the output voltage ܸ$V_{o}$ (in volts) is________.

For the voltage regulator circuit shown, the input voltage $(V_{in})$ is $20 V \pm 20\%$ and the regulated output voltage $(V_{out})$ is $10\: V.$ Assume the opamp to be ideal. For a load $R_L$ drawing $200\: mA,$ the maximum power dissipation in $Q_{1}\:\text{(in Watts)}$ is ________.