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Analog Circuits Training 1

Parmida Amngostar

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Objective: ��

To design a basic circuit that plays back the audio signal collected by a microphone

  • Microphone (audio signal source)
  • Speaker (to output the sound)

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Microphone and Analog Circuit

What is a microphone?�→ A transducer that converts sound waves into electrical signals.

What is a Speaker?�→ An actuator that converts electrical signals back into sound waves.

Why are analog circuits important in audio?�→ For amplification, filtering, and real-time signal processing

Real-world applications:�→ Audio recording, telecommunication, stethoscopes, smart assistants�

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Types of Microphone and Speaker

Common Microphone Types:

Dynamic – robust, no power needed, uses coil and magnet

Electret Condenser – compact, sensitive, needs a bias voltage

MEMS – tiny, integrated in smartphones and IoT devices

Common Speaker Types:

Dynamic Speakers – use coils and magnets (most common)

Piezoelectric Speakers – used in alarms/buzzers (high frequency)

Electrostatic Speakers – high fidelity, high voltage

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Components for ECG Circuit

  • Op-Amp
  • Speaker
  • Microphone
  • Capacitors
  • Resistor
  • Potentiometer
  • Breadboard
  • Wires

Op-Amp

Wires

Capacitor

Resistor & Potentiometer

Microphone & Speaker

Bread Board

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The Purpose of Each Component

Op-Amp

An operational amplifier (op-amp) is used in various analog circuits for amplification, signal processing, and other functions. 

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  • Capacitor

A capacitor's primary purpose is to store electrical energy in an electric field, acting as a temporary energy reservoir in electronic circuits. 

​

  • Resistor

A resistor is an electrical component that limits or regulates the flow of electrical current in an electronic circuit.

  • Potentiometer:

A potentiometer is a manually adjustable variable resistor with 3 terminals.

The Purpose of Each Component

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How Use Bread Board

Breadboards are composed of three (3) parts:

  1. Horizontal Rows (yellow and green lines)
  2. Vertical Columns
  3. Power (red) /Ground (blue) Rails

The middle divider separates both sides. So, if you wire power and ground to one side of the breadboard, you will also need to power/ground the other side.

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Circuit Schematic

  • Op-Amp: LM386
  • Speaker: 8ohm Dynamic Speaker
  • Electret Microphone
  • Capacitors: two 0.1uF, two 10uF, one 220uF
  • Resistor: two 10kΩ
  • Potentiometer: 10kΩ

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Required Systems for Measurement

  • DC Power Supply
  • Alligator clip Cables

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Wiring Up Step by Step

Step1: Op-amp placement and pinout check

From Datasheet

GND

GND

VCC

VCC

VCC

GND

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Wiring Up Step by Step

Step2: 10uF Capacitors Placement

Capacitor with Polarity:

The negative pin is marked as GRAY. Polarized capacitors must be connected with the correct orientation to function correctly and avoid damage. 

​

  • Num1(10uF CAP):

Positive pin: 1�Negative pin: 8

  • Num2(10uF CAP):

Positive pin: 7�Negative pin: GND

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Wiring Up Step by Step

Step3: 0.1uF and 10kΩ Components Placement

Capacitor without Polarity:

Non-polarized capacitors can be connected in either direction.

Resistors:

All resistors can be connected in either direction.

​

  • Num3(0.1uF CAP):

Between Pin 5 and an empty hole

  • Num4(10kΩ RES):

Between the chosen empty hole and GND

Empty

Hole

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Wiring Up Step by Step

Step4: 220uF Capacitor Placement

Capacitor with Polarity:

The negative pin is marked as GRAY.

​

  • Num5(220uF CAP):

Positive pin: 5�Negative pin: An empty hole

Empty

Hole

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Wiring Up Step by Step

Step5: Potentiometer Placement

Potentiometer (POT):

Place the three pins in three empty holes on the left side.

It should be placed similarly to the picture.

​

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Wiring Up Step by Step

Step6: 0.1uF and 10kΩ Components Placement

​

  • Num6(0.1uF CAP):

Between the left pin of the POT and an empty hole

  • Num7(10kΩ RES):

Between the chosen empty hole and GND

Empty

Hole

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Wiring Up Step by Step

Step7: Connect Wires

Connections:

  1. Pin 2 to GND
  2. Pin4 to GND
  3. Pin6 to VCC
  4. Right pin for POT to GND
  5. Pin 3 to middle pin of POT

​

(1)

(2)

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Wiring Up Step by Step

Step8: Connect the Microphone, Speaker, Power wires

Speaker:

Connect the red wire to the 220uF capacitor and the black wire to GND

Microphone:

Connect the red wire to the 0.1uF capacitor and the black wire to GND

Power Wires:

Connect two wires to VCC and GND

Microphone

Speaker

Power Wires

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Setting Up Power Supply

DC Power Supply

  1. Turn on the device
  2. Choose channel 2 🡪 Set to 5V 🡪 Push “Enter” pin
  3. Connect the “Black” output of channel 2 to GND
  4. Connect the “RED” output of channel 2 to VCC
  5. Push the “On” button for channels 2 & 3

(1)

(2.1)

(3)

(5)

(2.2)

(4)

VCC

GND

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Now, play