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Memory-based analog-based questions that appeared in Texas Instruments Interview. Try to solve similar kinds of questions in order to excel in your preparation level. The parameter values given in the questions to design may be different.

1. What should be the value of Zs that will transfer maximum power to the ZL? R=50 Ohms and L=5H.

Options

1. 50-jw5 Ohms
2. 50 Ohms
3. 60+jw5 Ohms
4. 0 Ohms

2. The Op-amp in the circuit shown below is an ideal op-amp. What is the output impedance Zout? if Rs=100 Ohms.

Options

1. 0 Ohms
2. 0.010 Ohms
3. 100 Ohms
4. Infinity

3. Op-amp in the below circuit is ideal. A sine wave of frequency 1mrad/s and amplitude of 1V is applied at Vin. What is the amplitude at node Vout? If R =100 Ohm, C=1nF, R’=500 Ohm.

Options

1. 6.0
2. 0.2
3. 2.0
4. 1.4

4. V1 is a non-ideal voltage source whose output voltage is measured to be Voc when no load is connected to its output. I1 is an ideal current source, which when shorted to ground forces a current of Isc through the short circuit.

The output impedance of V1 is 1kOhm and the output impedance of I1 is 9kOhm. If V1 and I1 are connected as shown below, what is the node voltage at node Vx (in volts). If Isc=50mA, Voc=5v.

Options

1. 49.50
2. 5.00
3. 0.00
4. 40.50

5. In the circuit shown below, VCC is connected to 3V. VIN and VINZ are complementary square wave signals with a high level of 3volt and a low level of 0volt.

A voltage step from 3volt to 0volt is applied at VIN (with the corresponding step from 0v to 3v applied at VINZ) at a time instant t=0. What is the time instant when the voltage at VOUT reaches 0.1v? If I=1mA, C=1pF, R=400 Ohm.

Options

1. 40*ln(10) ns
2. 40ns
3. 40*ln(4) ns
4. 0.30ns

6. In the circuit shown below, the capacitor is initially charged to 5v. The diodes shown are ideal with a forward drop of 1V when ON. Which of the following statements is true about the voltage waveform across the capacitor?

Options

1. It will remain at 5v
2. It will oscillate forever as a perfect sine wave
3. It will oscillate initially but then die down
4. It will oscillate forever but there will be voltage steps at the zero crossings

7. A capacitor used in the process technology has a symbol as shown in (a) and an equivalent representation as shown in (b) when connected between terminals 1 and 2.

Two capacitors are used in a circuit as shown in (c). What is the 3db bandwidth of the circuit between Vin(t) and Vo(t)? Assume that the buffer is ideal. Given C = 1 mF.

Options

8. For the circuit shown in the figure, what value of L (Inductor) will make the magnitude of V1 and V2 equal for all the frequencies? If C = 2 micro Farad, and R = 4 ohm.

Options

1. 16 micro Henry
2. 32 micro Henry
3. 5 micro Henry
4. 1 micro Henry

9. An ideal op-amp is used as a digital buffer as shown below. If the rise time at Vin(t) is 1ns, then the rise at Vo(t)?

Options

1. 0
2. 1ns
3. Depends on the value of C
4. You cannot use the Op-amp as the digital buffer.

10. A schematic of a buck converter is shown below. Vin is the DC input voltage. CTRL is a control signal that periodically switches ON and OFF. The control loop looks at the output voltage Vo and adjusts the duty cycle of CTRL to change Vo to the desired voltage. If Vo is to be set to 6v, the value of R is gradually increased.

What is the lowest value of R at which the inductor current touches 0 during the transient?

Assume that the current through the inductor is always higher than 0. Also assume that the capacitor is large enough that Vo is almost constant and the switching frequency of CTRL is 1 MHz and L = 1 mH, Vin = 10v.

Options

1. 50 kOhm
2. 500 kOhm
3. 500 Ohm
4. 5 kOhm

11. An amplifier has a non-linear response given by Vo = Vin + Vin^3 at all frequencies. When a sine wave of amplitude 1v is input to the amplifier, the output of the amplifier contains a harmonic at -80 dBm.

The amplifier output goes to a low pass filter with a 3db BW of 1MHz. What is the approximate amplitude of the harmonic at the output of the low pass filter if the input to the amplifier is a 3.33 MHz sine wave with an amplitude of 0.5v?

Options

1. -98 dB
2. -78 dB
3. -106 dB
4. -118 dB

12. A CMOS (Complementary Metal Oxide Semiconductor) inverter runs off a 3v supply (with the ground at 0v) and is loaded in three different ways as shown in fig (a),(b), and (c) below.

In (a), it is seen that the logic high level is 2.5v.

In (b), it is seen that the logic low level is 0.5v.

What is the expected logic high level in (c)?

Options

1. 3v
2. 57v
3. 5v
4. 75v

13. In the below diagram, VCC is a 3V supply. The block marked as Digital contains the digital running of the supply node marked as DVDD. For the purpose of estimating switching current, the digital block can be approximated as a capacitor 10 pF switching ON and OFF at the clock frequency (ON for half the period and OFF for the other half of the period).

The capacitor CDECAP is a decoupling capacitor with a value equal to 1000 pF and is used to smoothen the current ripple from VCC that is caused because of the digital block switching. If the resistor R is equal to 100 Ohm and the clock frequency for the digital block is 1 GHz, What is the value of DVDD?

Options

1. 5 Volts
2. 5 Volts
3. 3 Volts
4. 0 Volts

14. In the circuit below, the block marked as buffer provides a gain of 2 between its input and output. The Op-amp is an ideal Op-amp. The circuit is excited using an input waveform Vin(t) = 3 u(t).

The value of the resistor R is 1.5 Ohm and the value of the capacitance C is 1 F. The lowest voltage reached by Vo(t) is equal to:

Options

1. -6 Volts
2. 0 Volts
3. -3 Volts
4. -4.5 Volts

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