# Questions & Answers of Amplifiers - differential and operational

## Weightage of Amplifiers - differential and operational

Total 28 Questions have been asked from Amplifiers - differential and operational topic of Analog Circuits subject in previous GATE papers. Average marks 1.71.

Consider the constant current source shown in the figure below. Let $\beta$ represent the current gain of the transistor.

The load current I0 through RL is

The following signal Vi of peak voltage 8 V is applied to the non-inverting terminal of an ideal opamp. The transistor has $V_{BE}=0.7\;\mathrm V,\;\beta=100,\;V_{LED}=1.5\;\mathrm V,\;V_{CC}=10\;\mathrm V$ and $-V_{CC}=-10\;\mathrm V$ .

The number of times the LED glows is ________

An ideal opamp has voltage sources V1, V3, V5,...., VN-1 connected to the non-inverting input and V2,V4, V6,.....,VN connected to the inverting input as shown in the figure below (+VCC=15 volt,-VCC=-15 volt) The voltages V1, V2, V3, V4, V5, V6,… are 1, − 1/2, 1/3, −1/4, 1/5, −1/6, … volt, respectively. As N approaches infinity, the output voltage (in volt) is ___________

A p-i-n photodiode of responsivity 0.8A/W is connected to the inverting input of an ideal opamp as shown in the figure, +Vcc = 15 V, −Vcc = −15V, Load resistor RL = 10 kΩ. If 10 μW of power is incident on the photodiode, then the value of the photocurrent (in μA) through the load is ________

In the opamp circuit shown, the Zener diodes Z1 and Z2 clamp the output voltage V0 to +5 V or −5 V. The switch S is initially closed and is opened at time t=0.

The time t=t1 (in seconds) at which V0 changes state is ________

An opamp has a finite open loop voltage gain of 100. Its input offset voltage Vios (= +5mV) is modeled as shown in the circuit below. The amplifier is ideal in all other respects. Vinput is 25 mV.

The output voltage (in millivolts) is ________

For the circuit shown in the figure, R1 = R2 = R3 = 1 Ω, L = 1 μH and C = 1 μF. If the input Vin = cos(106t) , then the overall voltage gain (Vout /Vin) of the circuit is __________

In the circuit shown, assume that the opamp is ideal. The bridge output voltage V0 (in mV) for $\delta$ = 0.05 is ____.

In the bistable circuit shown, the ideal opamp has saturation levels of $±$V. The value of R1(in kΩ) that gives a hysteresis width of 500 mV is _________

Assuming that the opamp in the circuit shown below is ideal, the output voltage V0 (in volts)

For the voltage regulator circuit shown, the input voltage (Vin) is 20 ± 20% and the regulated output voltage (Vout) is 10 V. Assume the opamp to be ideal. For a load RL drawing 200 mA, the maximum power dissipation in Q1 (in Watts) is __________.

In the circuit shown using an ideal opamp, the 3-dB cut-off frequency (in Hz) is _____.

In the circuit shown, assume that the opamp is ideal. If the gain (Vo/Vin) is –12, the value of R (in kΩ) is ____.

In the low-pass filter shown in the figure, for a cut-off frequency of 5 kHz , the value of R2 (in kΩ) is _____________.

In the voltage regulator circuit shown in the figure, the op-amp is ideal. The BJT has VBE = 0.7 V and β  = 100, and the zener voltage is 4.7 V. For a regulated output of 9 V, the value of R (in Ω) is _______.

In the circuit shown, the op-amp has finite input impedance, infinite voltage gain and zero input offset voltage. The output voltage VOUT is

In the differential amplifier shown in the figure, the magnitudes of the common-mode and differential-mode gains are Acm and Ad, respectively. If the resistance RE is increased, then

Assuming that the Op-amp in the circuit shown is ideal, Vo is given by

The circuit shown represents

Assuming the OP-AMP to be ideal, the voltage gain of the amplifier shown below is

The transfer characteristic for the precision rectifier circuit shown below is (assume ideal OP-AMP and practical diodes)

In the circuit shown below, the op-amp is ideal, the transistor has VBE = 0.6 V and β = 150. Decide whether the feedback in the circuit is positive or negative and determine the voltage V at the output of the op-amp

Consider the following circuit using an ideal OPAMP. The I-V characteristics of the diode is described by the relation $I={I}_{o}\left({e}^{\frac{v}{{v}_{r}}}-1\right)$ where VT = 25mV, Io = 1$\mu$A and V is the voltage across the diode (taken as positive for forward bias).

For an input voltage Vi = -1V, the output voltage Vo is

The OPAMP circuit shown above represents a

For the Op-Amp circuit shown in the figure, Vo is

In the Op-Amp circuit shown, assume that the diode current follows the equation I = IS exp(V/VT). For Vi = 2 V, Vo = Vo1 and for Vi = 4 V, Vo = Vo2. The relationship between Vo1 and Vo2 is

Consider the Op-Amp circuit shown in the figure.

The transfer function V0(s)/Vi(s) is

If ${V}_{i}={V}_{1}\mathrm{sin}\left(\omega t\right)$ and $V_o=V_2\sin\left(\omega t+\phi\right)$, then the minimum and maximum values of $\phi$ (in radians) are respectively