# Electronic Devices and Circuits Questions and Answers – Transistors Millers Theorem

This set of Electronic Devices and Circuits Multiple Choice Questions & Answers (MCQs) focuses on “Transistors Millers Theorem”.

1. What technique is used in Millers Theorem?
a) Two-port network
b) Hybrid parameters
c) Grounding
d) Short circuiting

Explanation: In Millers Theorem, we use the equivalent two-port network of the given electrical circuit. We divide the circuit into two parts, each part representing a different port for easier analysis of the circuit.

2. Which law is the Millers Theorem based on?
a) Ohm’s Law
b) Moore’s Law
c) Coulomb’s Law
d) Kirchhoff’s Current and Voltage Law

Explanation: The Millers Theorem deals with the impedance supplied by two current/voltage sources connected in parallel. These two versions were derived by Kirchhoff’s two laws: Voltage and Current laws. The dual Millers Theorem is based mainly on the current laws while the other theorem focuses on the voltage law.

3. According to Millers Theorem, what should be the configuration of voltages?
a) Both dependent voltages
b) Both independent voltages
c) One dependent voltage and one independent voltage
d) No specification necessary

Explanation: Miller theorem proposes that an impedance segment is provided by two irregular voltage sources that are associated in arrangement through the common ground. For all intents and purposes, one of them goes about as an autonomous voltage source and different demonstrations a directly reliant voltage.

4. What is theimpedance from the input port according to Millers Theorem?
a) Zin1 = Z × K / 1 – K
b) Zin1 = Z × K / 1 + K
c) Zin1 = Z / 1 – K
d) Zin1 = Z / 1 + K

Explanation: According to Millers Theorem, to calculate the input impedance from the input port we use: Zin1 = Z / 1 – K. Where, Z is the original circuit impedance and K is the ratio of the two nodal voltages V2 / V1.

5. What is the impedance from the output port according to Millers Theorem?
a) Zin2 = Z × K / K – 1
b) Zin2 = Z × K / K + 1
c) Zin2 = Z / K – 1
d) Zin2 = Z / K +1

Explanation: According to Millers Theorem, to calculate the input impedance from the output port we use: Zin2 = Z × K / K – 1. Where, Z is the original circuit impedance and K is the ratio of the two nodal voltages V2 / V1.
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6. According to Millers Theorem, what is the impedance in input port if I1 = 20 mA, I2 = 30 mA and Z = 2.3 kΩ?
a) 0.38 kΩ
b) 3.83 kΩ
c) 0.57 kΩ
d) 5.75 kΩ

Explanation: To calculate theimpedance in input port, given I1 = 20 mA, I2 = 30 mA and Z = 2.3 kΩ:
Zin1 = (1 + α) × Z
α = I2 / I1 = 1.5
Zin1 = (1 + α) × Z = (1 + 1.5) × 2.3 = 5.75 kΩ.

7. According to Millers Theorem, what is the impedance in output port if I1 = 20 mA, I2 = 30 mA and Z = 2.3 kΩ?
a) 0.38 kΩ
b) 3.83 kΩ
c) 0.57 kΩ
d) 5.75 kΩ

Explanation: To calculate theimpedance in output port, given I1 = 20 mA, I2 = 30 mA and Z = 2.3 kΩ:
Zin2 = (1 + α) × Z / α
α = I2 / I1 = 1.5
Zin2 = (1 + α) × Z / α = (1 + 1.5) × 2.3 / 1.5 = 3.83 kΩ.

8. What are the applications of Millers Theorem?
a) Lower power consumption
d) Circuit optimization

Explanation: Millers Theorem is applied in an amplifier setting known as Millers amplifier. The amplifier can be used as an additional voltage source which converts the actual impedance into a virtual impedance. The virtual impedance can be thought of as a component connected in parallel to the amplifier input.

Sanfoundry Global Education & Learning Series – Electronic Devices and Circuits.