1. Consider the following circuit using an ideal OP-AMP. The I-V characteristic of the diode is described by the relation I = I_{o}(exp(V/V_{T}) - 1), where VT = 25 mV, I_{o} = 1 µA and V is the voltage across the diode(taken as positive for forward bias). For an input voltage V_{i} = - 1 volts, the output voltage V_{o} is

3. Consider the schmitt trigger circuit shown below.

A triangular wave which goes from –12 volts to +12 volts is applied to the inverting input of OP-AMP. Assume that the output of the OP-AMP swings from +15 volts to –15 volts. The voltage at the non-inverting input switches between
a. – 12 volts and +12 volts
b. – 7.5 volts and +7.5 volts
c. – 5 volts and +5 volts
d. 0 volts and +5 volts

Statement for Linked Answer Question:
In the following transistor circuit, V_{BE} = 0.7 volts, r_{e} = 25 mV/I_{E}, β and all the capacitances are very large.

4. The value of DC current I_{E} is
a. 1 mA
b. 2 mA
c. 5 mA
d. 10 mA

Answer:A

5. The mid-band voltage gain of the amplifier is approximately
a. – 180
b. – 120
c. – 90
d. – 60

2. In the circuit shown below, the OP-AMP is ideal, the transistor has V_{BE} = 0.6 volts 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.

a. Positive feedback, V = 10 Volts
b. Positive feedback, V = 0 Volts
c. Negative feedback, V = 5 Volts
d. Negative feedback, V = 2 Volts

3. A small signal source Vi(t) = Acos20t + Bsin10^{6}t is applied to a transistor amplifier as shown below. The transistor has β = 150 and h_{ie} = 3 KΩ. Which expression best approximate V_{o}(t).

a. V_{o}(t) = - 1500 (Acos20t + Bsin10^{6}t)
b. V_{o}(t) = - 150 (Acos20t + Bsin10^{6}t)
c. V_{o}(t) = - 1500 (Bsin10^{6}t)
d. V_{o}(t) = - 150 (Bsin10^{6}t)

1. The amplifier circuit shown below uses a silicon transistor. The capacitors C_{C} and C_{E} can be assumed to be short at signal frequency and effect of output resistance r_{o} can be ignored. If C_{E} is disconnected from the circuit, which one of the following statements is TRUE.

a. The input resistance R_{i} increases and magnitude of voltage gain A_{V} decreases
b. The input resistance R_{i} decreases and magnitude of voltage gain A_{V} increases
c. The input resistance R_{i} decreases and magnitude of voltage gain A_{V} decreases
d. The input resistance R_{i} increases and magnitude of voltage gain A_{V} increases

2. In the silicon BJT circuit shown below, assume that the emitter area of transistor Q_{1} is half that of transistor Q_{2}. The value of current I_{o} is approximately

1. In the circuit shown below, capacitors C_{1} and C_{2} are very large and are shorts at the input frequency . v_{i} is a small signal input. The gain magnitude |V_{0}/V_{i}| at 10 M rad/sec is

2. The circuit below implements a filter between the input current i_{i} and the output voltage v_{o}. Assume that the op-amp is ideal. The filter implemented is a

a. Low pass filter
b. Band pass filter
c. Band stop filter
d. High pass filter

Statement for linked answer Questions (3 and 4):
In the circuit shown below, assume that the voltage drop across a forward biased diode is 0.7 votls. The thermal voltage V_{T} = KT/q = 25 mV. The small signal input v_{i} = 100 cos(ωt) mV.

3. The bias current I_{DC} through the diodes is
a. 1 mA
b. 1.28 mA
c. 1.5 mA
d. 2 mA

Answer:A

4. The ac output voltage V_{AC} is
a. 0.25 cos(ωt) mV
b. 1 cos(ωt) mV
c. 2 cos(ωt) mV
d. 22 cos(ωt) mV

1. The current i_{b} through the base of a silicon NPN transistor is 1+0.1cos (10000πt) mA. At 300^{o}K, the r_{π} in the small signal model of the transistor is ________ (in Ohms).