Block Diagrams

Block diagrams are used to understand (and design) complete circuits by breaking them down into smaller sections or blocks. Each block performs a particular function and the block diagram shows how they are connected together. No attempt is made to show the components used within a block, only the inputs and outputs are shown. This way of looking at circuits is called the systems approach.
Power supply (or battery) connections are usually not shown on block diagrams.

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Audio Amplifier System

The power supply (not shown) is connected to the pre-amplifier and power amplifier blocks.

• Microphone - a transducer which converts sound to voltage.
• Pre-Amplifier - amplifies the small audio signal (voltage) from the microphone.
• Tone and Volume Controls - adjust the nature of the audio signal.
  The tone control adjusts the balance of high and low frequencies.
  The volume control adjusts the strength of the signal.
• Power Amplifier - increases the strength (power) of the audio signal.
• Loudspeaker - a transducer which converts the audio signal to sound.

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Radio Receiver System

The power supply (not shown) is connected to the audio amplifier block.

• Aerial - picks up radio signals from many stations.
• Tuner - selects the signal from just one radio station.
• Detector - extracts the audio signal carried by the radio signal.
• Audio Amplifier - increases the strength (power) of the audio signal.
  This could be broken down into the blocks like the Audio Amplifier System shown above.
• Loudspeaker - a transducer which converts the audio signal to sound.

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Regulated Power Supply System

• Transformer - steps down 230V AC mains to low voltage AC.
• Rectifier - converts AC to DC, but the DC output is varying.
• Smoothing - smooths the DC from varying greatly to a small ripple.
• Regulator - eliminates ripple by setting DC output to a fixed voltage.

For futher information please see the Power Supplies page.

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Feedback Control System

The power supply (not shown) is connected to the control circuit block.

• Sensor - a transducer which converts the state of the controlled quantity to an electrical signal.
• Selector (control input) - selects the desired state of the output. Usually it is a variable resistor.
• Control Circuit - compares the desired state (control input) with the actual state (sensor) of the controlled quantity and sends an appropriate signal to the output transducer.
• Output Transducer - converts the electrical signal to the controlled quantity.
• Controlled Quantity - usually not an electrical quantity, e.g. motor speed.
• Feedback Path - usually not electrical, the Sensor detects the state of the controlled quantity.