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Bias Compensation Using Diode & Transistor | Analog and Digital Electronics - Electrical Engineering (EE) PDF Download

BIAS COMPENSATION USING DIODE AND TRANSISTOR:

DIODE COMPENSATION:

                                            Bias Compensation Using Diode & Transistor | Analog and Digital Electronics - Electrical Engineering (EE)

 

The following fig 4.8 shows a transistor amplifier with a diode D connected across the base-emitter junction for compensation of change in collector saturation current ICO. The diode is of the same material as the transistor and it is reverse biased by e the emitter-base junction voltage VBE, allowing the diode reverse saturation current IO to flow through diode D. The base current IB=I-IO.

As long as temperature is constant, diode D operates as a resistor. As the temperature increases, ICO of the transistor increases. Hence, to compensate for this, the base current IB should be decreased.

The increase in temperature will also cause the leakage current IO through D to increase and thereby decrease the base current IB. This is the required action to keep Ic constant.

This type of bias compensation does not need a change in Ic to effect the change in IC, as both IO and ICO can track almost equally according to the change in temperature.        

THERMISTOR COMPENSATION:

The following fig 4.9 a thermistor RT, having a negative temperature coefficient is connected in parallel with R2. The resistance of thermistor decreases exponentially with increase of temperature. An increase of temperature will decrease the base voltage VBE, reducing IB and IC.

                                       Bias Compensation Using Diode & Transistor | Analog and Digital Electronics - Electrical Engineering (EE)

SENSISTOR COMPENSATION:

In the following fig 4.10 shown a sensistor Rs having a positive temperature coefficient is connected across R1 or RE. Rs increases with temperature. As the temperature increases, the equivalent resistance of the parallel combination of R1 and Rs also increases and hence VBE decreases, reducing Iand Ic. This reduced Ic compensates for increased Ic caused by the increase in VBE, ICO and β due to temperature.

Bias Compensation Using Diode & Transistor | Analog and Digital Electronics - Electrical Engineering (EE)

                                         Bias Compensation Using Diode & Transistor | Analog and Digital Electronics - Electrical Engineering (EE)

The document Bias Compensation Using Diode & Transistor | Analog and Digital Electronics - Electrical Engineering (EE) is a part of the Electrical Engineering (EE) Course Analog and Digital Electronics.
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FAQs on Bias Compensation Using Diode & Transistor - Analog and Digital Electronics - Electrical Engineering (EE)

1. What is bias compensation in electronic circuits?
Ans. Bias compensation in electronic circuits refers to the techniques used to ensure stable and accurate operation of the circuit by minimizing any variations caused by temperature changes or component aging. It involves the use of diodes and transistors to compensate for any biases that may affect the performance of the circuit.
2. How does a diode help in bias compensation?
Ans. A diode can be used in bias compensation by providing a temperature-dependent voltage drop. By connecting a diode in series with a resistor, the voltage drop across the diode changes with temperature, compensating for any variations in the circuit's bias caused by temperature changes. This helps maintain the desired operating conditions of the circuit.
3. What role does a transistor play in bias compensation?
Ans. Transistors can be used in bias compensation by acting as active devices that automatically adjust their characteristics to compensate for temperature variations or component aging. By using a transistor in a feedback loop, its characteristics can be utilized to counteract any changes in the bias conditions of the circuit, ensuring stable and accurate operation.
4. What are the advantages of bias compensation using diode and transistor?
Ans. Bias compensation using diode and transistor offers several advantages. Firstly, it helps maintain stable and accurate operation of electronic circuits by compensating for variations caused by temperature changes or component aging. Secondly, it improves the reliability and longevity of the circuit by minimizing the impact of these variations. Lastly, it allows for better control and optimization of circuit parameters, leading to improved overall performance.
5. Can bias compensation techniques be used in all electronic circuits?
Ans. Bias compensation techniques using diode and transistor can be applied to a wide range of electronic circuits. However, the suitability of these techniques depends on the specific requirements and characteristics of the circuit. In some cases, alternative methods may be more appropriate, such as using temperature sensors or specialized integrated circuits designed for bias compensation. It is important to analyze the circuit and its operating conditions to determine the most effective bias compensation approach.
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