MIKROE-957 mikroElektronika, MIKROE-957 Datasheet - Page 48

• Manufacturer Part Number: MIKROE-957
• Description: Other Development Tools ASLK PRO ANALOG DEVELOPMENT SYSTEM
• Manufacturer: mikroElektronika

Specifications of MIKROE-957

• Rohs: yes
• Product: Analog System Lab Kit PRO
• Tool Is For Evaluation Of: TL082, MPY634
• Operating Supply Voltage: 2.5 V to 5.5 V
• Description/function: Analog Lab Kit for Undergraduate Engineering
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 40 C

The reader will benefit from the recorded lectures at [25]. Another useful reference
is the application note on Automatic Level Controller for Speech Signals using PID
Controllers [2].
In the signal chain of an electronic system, the output of the sensor can vary
depending on the strength of the input. To adapt to wide variations in the magnitude
of the input, we can design an amplifier whose gain can be adjusted dynamically.
This is possible when the input signal has a narrow bandwidth and the control
system is called Automatic Gain Control or AGC. Since we may wish to maintain the
output voltage of the amplifier at a constant level, we also use the term Automatic
Volume Control (AVC). Figure 8.1 shows an AGC circuit. The typical I/O characteristics
of AGC/AVC circuit is shown in Figure 8.2. As shown in Figure 8.2, the output value
of the system remains constant at
Design AGC/AVC system to maintain the peak amplitude of the sine wave at 2V.
page 48
8.1 Brief theory and motivation
8.2 Specification
In the front-end electronics of a system, we may require that the gain of the
amplifier be adjustable, since the amplitude of the input keeps varying. Such
a system can be designed using feedback. This experiment demonstrates
one such system.
Figure 8.1: Automatic Gain Control (AGC)/Automatic Volume Control (AVC)
V
Goal of the experiment
I
=Vpi•sinωt
V
C
]
V
V
C
R
]
Vpi•sinωt
V
pi
2
=
V V
r
ref
2
beyond input voltage
V V
R
r
ref
]
V
C
V
•Vpi
R
C
]
Vref=
2
V
1
R
2V
V
OP
R
2
V
pi
2
V V
=
r
ref
2
V V
r
ref
.
8.3 Measurements to be taken
Transfer Characteristics - Plot the input versus output characteristics for the AGC/AVC.
8.4 What you should submit
1
2
3
Simulate the circuit of Figure 8.1 and obtain the Transfer Characteristic of the
system. Assume that the input comes from a function generator; use a sine
wave input of a single frequency.
Build the circuit shown on Figure 8.1. Plot/print the transfer characteristic
using the oscilloscope and compare it with simulation results.
Plot the output as a function of input voltage. Enter sufficient number of
readings in Table 8.2. Does the output remain constant as the magnitude of
the input is increased? Beyond what value of the input voltage does the gain
begin to stabilize? We have included sample output waveform for the AGC
circuit in Figure 8.3.
S.No.
1
2
3
4
Figure 8.2: Input-Output Characteristics of AGC/AVC
Table 8.1: Transfer characteristic of the AGC circuit
Input Voltage
Analog System Lab Kit PRO
Output Voltage