Imagine a volume knob that adjusts itself, this circuit is just like that.
It listens to the incoming sound like music or a voice and automatically turns it up or down to a comfortable level.
So if the music is quiet it gets a little bit louder.
And if the music is really loud it gets a little bit quieter.
This is handy so you do not have to constantly adjust the volume yourself.
Circuit Working:
Parts list:
| Category | Description | Quantity | Notes |
|---|---|---|---|
| Resistors | 10k | 1 | 1/4 watt |
| 4.7k | 1 | 1/4 watt | |
| 1k | 1 | 1/4 watt | |
| 4.7M | 1 | 1/4 watt | |
| 47k | 2 | 1/4 watt | |
| Potentiometer | 100k | 1 | |
| Capacitors | Ceramic 0.015μF | 2 | |
| Ceramic 0.01μF | 1 | ||
| Ceramic 0.1μF | 1 | ||
| Electrolytic | 100μF 16V | 1 | |
| 10μF 16V | 1 | ||
| Semiconductors | IC LM358 | 1 | |
| 2SC733 or 2N2222 | 2 |
Op amp A1 functions as an input signal buffer.
Removing diodes D1 and D2 transforms A1 into an amplifier.
A1 is DC bias is established through R4 and C5 a technique allowing A2 to cap the DC level at its input limiting amplification to a maximum of 100 times.
The offset bias remains relatively constant.
The amplified signal is directed to regulator diodes D1 and D2 through transistors T1 and T2 with trimmer P1 regulating this sampled signal.
Increased signal strength leads to higher current flow through the diodes.
These regulator diodes exhibit a non linear curve with decreasing resistance as current increases.
The input signal is more or less grounded through the diodes functioning as an attenuator that intensifies as the current through the diodes rises.
Formula:
Operational amplifiers, or op-amps, are used in Automatic Gain Control AGC circuits, which are intended to maintain a generally constant output signal level in spite of amplitude changes in the input signal.
Here is a basic explanation of how to use an op amp and the related formula to create AGC
The objective of an op amp based AGC circuit is to dynamically modify the op amp strength in response to the level of the input signal.
This is usually accomplished by controlling the gain of the amplifier stage by feeding back a part of the output signal.
In a circuit like this, the precise formula for AGC gain control is as follows:
Output Voltage = G * (Input Voltage)
where,
- G: the gain factor, is modifiable in real time according to the AGC control signal obtained from the output level.
Depending on the needs and particular design of the AGC circuit, the precise gain adjustment and AGC control method may change.
Additional parts like resistors for bias level adjustment, capacitors for smoothing and diodes for rectification are frequently included in practical implementations.
Simulation tools and in depth circuit analysis are frequently utilized for accurate AGC design in order to maximize performance metrics including noise performance, gain stability and response time.
How to Build:
Building an Automatic Volume Control AVC circuit requires a good understanding of electronics and circuit design.
Op Amp A1 as Input Buffer:
- Connect Op Amp A1 to act as an input buffer.
DC Biasing:
- Use resistors R4 and capacitor C5 for DC biasing.
Diodes D1 and D2:
- Connect diodes D1 and D2.
- These diodes serve as regulator diodes.
Transistors T1 and T2:
- Connect transistors T1 and T2.
- These transistors are used to control the current through the diodes.
Trimmer P1:
- Connect trimmer potentiometer P1 to control the sample signal.
Output:
- The amplified signal is then directed to the output.
Additional Considerations:
- Ensure that the circuit is powered appropriately.
- Use a stable power supply within the operational range of the components.
Component Values:
- Choose resistor, capacitor and diode values based on the desired characteristics of your AVC circuit.
- Component values will depend on the specific requirements of your application.
- Test the circuit on a breadboard before soldering components onto a PCB.
Amplification Range:
- Adjust resistor values and potentially include additional components to control the amplification range as needed.
Noise Considerations:
- Take measures to minimize noise especially if the circuit is intended for high fidelity applications.
Note:
Building electronic circuits involves risks and it is important to follow safety precautions.
If you are not experienced with electronics consider seeking assistance from someone with expertise in circuit design or consulting relevant resources like electronics textbooks or online tutorials.
Conclusion:
AVC circuits are commonly used in audio devices like radios, televisions and amplifiers.
They help ensure that the volume level remains consistent preventing sudden loudness changes when switching between different radio stations or audio sources.