# Electronic Devices and Circuits Questions and Answers – Two-Port Devices and Hybrid Model

This set of Electronic Devices and Circuits Multiple Choice Questions & Answers (MCQs) focuses on “Two-Port Devices and Hybrid Model”.

1. How many terminals does a two – port network have?
a) 2
b) 4
c) 6
d) 8

Explanation: A two – port network has four terminals, two input terminals and two output terminals. Each pair of input or output terminals consist of a current and voltage terminal. In a two – port network, port 1 is usually the input terminal while port 2 is the output terminal.

2. What is the most efficient way to calculate voltage or current in a two – port network?
a) Z parameters
b) Y parameters
c) H parameters
d) G parameters

Explanation: We use H parameters or hybrid parameters to calculate the voltage or current of a two – port network. Z parameters stand for impedance parameters, Y parameters stand for admittance parameters and G parameters stand for inverse hybrid parameters.

3. What is the size of a h parameter matrix for a two – port network?
a) 2 × 2
b) 2 × 4
c) 4 × 4
d) 4 × 2

Explanation: The hybrid parameters for a two – port network consist of a 2 × 2 matrix consisting of four elements: h11, h12, h21 and h22. They are calculated by short circuiting the input / output port and calculating the respective ratios.

4. What are the units of the off – diagonal h parameters?
a) Volt
b) Ampere
c) dimensionless
d) Ohm

Explanation: The off – diagonal elements of the hybrid parameter matrix are dimensionless. One of the diagonal parameters is measured in ohm while the other diagonal parameter is measured in mho.

5. How many types of parameters are used for two port networks?
a) 8
b) 1
c) 2
d) 6

Explanation: There are essentially 6 different parameters involving two – port networks. They are Z parameter (impedance), Y parameter (admittance), T parameter (transmission), T’ parameter (inverse transmission), H parameter (hybrid) and G parameter (inverse hybrid).
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6. How do we calculate V1 in a two – port network?
a) V1 = h21I2 + h22V2
b) V1 = h11I1 + h12V2
c) V1 = h11I2 + h12V2
d) V1 = h21I1 + h22V2

Explanation: We use the hybrid matrix parameters to calculate the input output voltage and current of the two ports. V1 is the input voltage from the first port and it is calculated using the formula: V1 = h11I1 + h12V2.

7. What is the value of I2 if h21 = 2, I1 = 1A, h22 = 0.04 and V2 = 50V?
a) 2A
b) 0.2A
c) 0.4A
d) 4A

Explanation: To find the current I2 we use the below mentioned formula. Given values are h21 = 2, I1 = 1A, h22 = 0.04 and V2 = 50V.
I2 = h21I1 + h22V2
I2 = (2) × (1) + (0.04) × (50) = 2 + 2 = 4A.

8. At what frequency range do hybrid models work the best?
a) Very low frequency
b) Low to moderate frequency
c) Moderate to high frequency
d) High frequency

Explanation: Hybrid models with varying current and voltage work best at low to moderate frequencies. At higher frequencies, we use power and energy variables instead of the current and voltage variables.

9. Hybrid parameters were also called “Series – parallel parameters”.
a) True
b) False

Explanation: Hybrid parameters or h parameters were initially called series – parallel parameters. Later they were renamed as hybrid parameters due to their ability to adapt to the physical characteristics of transistors.

10. Why are h parameters used for transistor calculations?
a) Ease of use
b) Ease of use, easy to measure
c) It is not used for transistor calculations
d) Easy to measure

Explanation: H parameters are widely used for transistor calculations for multiple reasons. It is easier to use since in some cases we are unable to calculate the Z and Y parameters. It is also easy to measure since most transistor manufacturers mention the h parameters, else it is easy to calculate from the static characteristic curve.

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