Table of Contents
ToggleAim
To calculate and verify Hybrid parameters of two-port network.
Apparatus
Breadboard, Batteries or DC regulated power supply, Resistors, Digital multimeter, Connecting wires, Alligator clips.
Theory
h-Parameters of Two Port Network are also called hybrid parameters. These parameters are very useful in constructing models for transistors.
These parameters are obtained by expressing voltage at input port and the current at output port in terms of the current at the input port and the voltage at the output port.
We will get the following set of two equations by considering the variables V_{1}& I_{2}as dependent and I_{1}& V_{2} as independent.
In equation form, above relations can be written as,
V_{1}=h_{11}I_{1}+h_{12}V_{2} …(1)
I_{2}=h_{21}I_{1}+h_{22}V_{2} …(2)
The coefficients of independent variables, I_{1}and V_{2}, are called ash-parameters.
In matrix form the above equations can be written as,
Assuming the short circuit condition at the output terminal, we get V_{2}= 0
Now putting V_{2}= 0 in (1), we get
V_{1}= h_{11}I_{1}
∴h_{11}= (V_{1}/ I_{1})
Similarly, putting V_{2}= 0 in (2), we get
I_{2}= h_{21}I_{1}
∴ h_{21}= (I_{2}/ I_{1})
Again, assuming input port of the two-port network to be open circuited, the input voltage will be zero i.e. I_{1}= 0
Now putting I_{1}= 0 in (1), we get
V_{1}= h_{12}V_{2}
∴ h_{12}= (V_{1}/ V_{2})
Similarly putting I_{1}= 0 in (3), we get
I_{2}= h_{22}V_{2}
∴ h_{22}= (I_{2}/ V_{2})
Thus, there are four h parameter for a two-port or four-terminal network. Their values are tabulated below.
h_{11} | (V_{1}/ I_{1}) | Condition: Output port of the two-port network is short circuited i.e. V_{2}= 0 |
h_{21} | (I_{2}/ I_{1}) | |
h_{12} | (V_{1}/ V_{2}) | Condition: Input port of the two-port network is open circuited i.e. I_{1}= 0 |
h_{22} | (I_{2}/ V_{2}) |
The individual h-parameters are defined as follows,
This is called short circuit input impedance.
This is called forward short circuit current gain.
This is called reverse open circuit voltage gain.
This is called open circuit output admittance.
The parameters, h_{12}and h_{21}, do not have any units, since those are dimension-less. The units of parameters, h_{11}and h_{22}, are Ohm and Mho respectively.
All above parameters are having different units such as ohm for short circuit impedance and mho for open circuit output admittance, the name of the parameter is hybrid parameter.
Circuit Diagram
[Chose any resistor between 200Ω to 2KΩ and DC supply beween 5V to 12V]
Procedure
- Connect the circuit as shown in figure 2.
- First short the output port (port 2) and supply 10V to input port (port 1). Measure output current and input current using multi-meter.
- Secondly, open circuit input port and supply 5V to output port. Measure input and output voltages and output current using multi-meter.
- Calculate the values of h-parameters using respective formulas (Shown in calculation section).
- Switch ‘OFF’ the supply after taking the readings.
Precautions
- Before circuit connection working condition of all the components must be checked.
- All the connection should be tight.
- Ammeter must be connected in series while voltmeter must be connected in parallel to the components (resistors).
- The electrical current should not flow the circuit for long time, otherwise its temperature will increase and the result will be affected.
Observation table
When output port is short circuited | When input port is open circuited | ||||
V_{1} | I_{1} | I_{2} | V_{1} | V_{2} | I_{2} |
Calculations
For Practical Values:
(a) When output is short circuited i.e. V_{2} = 0
h_{11}= V_{1}/ I_{1} = ___ Ω
h_{21}= I_{2}/ I_{1 }= ___
(b) When input is open circuited i.e. I_{1} = 0
h_{12}= V_{1}/ V_{2 }= ___
h_{22}= I_{2}/ V_{2 }= ___ mho
For Theoretical Values:
[Use any method to calculate h-parameters]
h_{11} = ____ Ω
h_{21}= ____
h_{12}= ____
h_{22}= ____mho
Result
Parameter→ | h_{11} | h_{12} | h_{21} | h_{22} |
Theoretical | ||||
Practical |
Conclusion
Calculated and practical values of h-parameters are found to be nearly equal hence h-parameters are verified.
Video Tutorial on H-Parameters
For Calculation to Verify Hybrid parameters of two-port network
Recent posts
Related posts:
- Verification of Nortons Theorem
- Verification of Kirchhoffs Laws
- Verification of Superposition Theorem
- Verification of Thevenins theorem
- Verification of Maximum Power Transfer Theorem
- Verify Z-Parameters of Two-port Network
- Verify Y-Parameters of Two-port Network
- Study the transient response of a series RC circuit
- Study the transient response of a series RL circuit
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