Analog communication manual

am generation using ift

The collector current is inversely proportional to the base voltage. The oscillator output has amplitude 10VPP.

Automatic Gain Control trainer kit. Hence when the output goes high the collector current goes low. To get SSB upper side band signal, connect the output of the balanced modulator to the summer circuit.

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The output from the VGA can be further amplified by a second stage to generate and adequate level of Vo. If the signal level changes are much slower than the information rate contained in the signal, then an AGC circuit can be used to provide a signal with a well defined average level to downstream circuits.

This amplitude can be varied using the potentiometers provided.

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The x-axis is the input amplitude and the y-axis is the output voltage. Variable-gain amplifiers are controlled electrically, and when attenuators are used in receivers, they are often operated electrically either by variable voltages for continuous attenuators or by electric switches relays or diodes for fixed or stepped attenuators. Hence the input that is given to the inverting input of the OP-Amp is biased about the mean value of the supply Vcc. The output of the AGC is then given to the power amplifier via a variable resistor. Thus the output is controlled automatically depending on the input. After V1 the output remains fairly constant for change in the input till V2. Automatic Gain Control AGC circuits are employed in many systems where the amplitude of an incoming signal can vary over a wide dynamic range. This amplitude can be varied using the potentiometers provided. Automatic Gain Control trainer kit. The BJT acts as a switch which sources or sinks the collector current based on the base voltage.

Variable-gain amplifiers are controlled electrically, and when attenuators are used in receivers, they are often operated electrically either by variable voltages for continuous attenuators or by electric switches relays or diodes for fixed or stepped attenuators.

Hence the voltage at the inverting input also goes low.

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Measure and record the SSB signal frequency. The output of the AGC is then given to the power amplifier via a variable resistor. When the input amplitude is given it is biased about the mean value of the supply. In most system applications, the time to adjust the gain in response to an input amplitude change should remain constant, independent of the input amplitude level and hence gain setting of the amplifier. Variable-gain amplifiers are controlled electrically, and when attenuators are used in receivers, they are often operated electrically either by variable voltages for continuous attenuators or by electric switches relays or diodes for fixed or stepped attenuators. The BJT acts as a switch which sources or sinks the collector current based on the base voltage. To get SSB upper side band signal, connect the output of the balanced modulator to the summer circuit. First the output is coupled to the variable resistor with the help of a coupling capacitor. Hence the input that is given to the inverting input of the OP-Amp is biased about the mean value of the supply Vcc. The resistance is directly proportional to the gate voltage, which is in-turn proportional to the collector current of the BJT. Check the connections before giving the power supply 2. This amplitude can be varied using the potentiometers provided. Connect the circuit as shown in the figure. The oscillator output has amplitude 10VPP.

First the output is coupled to the variable resistor with the help of a coupling capacitor. Variable gain control for the later stages can operate from low signal levels.

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Also the output is fed back to the inverting input coupled with the audio input by means of an active network. Automatic Gain Control AGC circuits are employed in many systems where the amplitude of an incoming signal can vary over a wide dynamic range.

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There are 2 outputs from the RF generator, one is direct output and another is 90o out of phase with the direct output. After V1 the output remains fairly constant for change in the input till V2. It is used for scaling the output. The large dynamic range of signals that must be handled by most receivers requires gain adjustment to prevent overload or IM of the stages and to adjust the demodulator input level for optimum operation. The OP-Amp acts as an amplifier with positive feedback. Automatic Gain Control trainer kit. Set the AF signal amplitudes to 8 Vp-p using amplitude control and connect to the balanced modulators.
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Analog communications lab manual