05-12-2012, 02:26 PM
147352 ELECTRONIC CIRCUITS LAB I LAB MANUAL
FIXED BIAS AMPLIFIER CIRCUIT
AIM:
To construct a fixed bias amplifier circuit and to plot the frequency response characteristics.
THEORY:
In order to operate the transistor in the desired region, we have to apply an external dc voltage of correct polarity and magnitude to the two junctions of the transistor. This is called biasing of the transistor.
When we bias a transistor, we establish certain current and voltage conditions for the transistor. These conditions are called operating conditions or dc operating point or quiescent point. This point must be stable for proper operation of transistor. An important and common type of biasing is called Fixed Biasing. The circuit is very simple and uses only few components. But the circuit does not check the collector current which increases with the rise in temperature.
PROCEDURE
1. Connections are made as per the circuit diagram.
2. The waveforms at the input and output are observed for Class A, Class B and Class C operations by varying the input voltages.
3. The biasing resistances needed to locate the Q-point are determined.
4. Set the input voltage as 1V and by varying the frequency, note the output voltage.
5. Calculate gain=20 log (Vo / Vin)
6. A graph is plotted between frequency and gain.
FIXED BIAS AMPLIFIER CIRCUIT
AIM:
To construct a fixed bias amplifier circuit and to plot the frequency response characteristics.
THEORY:
In order to operate the transistor in the desired region, we have to apply an external dc voltage of correct polarity and magnitude to the two junctions of the transistor. This is called biasing of the transistor.
When we bias a transistor, we establish certain current and voltage conditions for the transistor. These conditions are called operating conditions or dc operating point or quiescent point. This point must be stable for proper operation of transistor. An important and common type of biasing is called Fixed Biasing. The circuit is very simple and uses only few components. But the circuit does not check the collector current which increases with the rise in temperature.
PROCEDURE
1. Connections are made as per the circuit diagram.
2. The waveforms at the input and output are observed for Class A, Class B and Class C operations by varying the input voltages.
3. The biasing resistances needed to locate the Q-point are determined.
4. Set the input voltage as 1V and by varying the frequency, note the output voltage.
5. Calculate gain=20 log (Vo / Vin)
6. A graph is plotted between frequency and gain.