This is the block diagram of the most of regulated power supply.

Notes:

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

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This is the block diagram of an completed audio amplifier from input (microphone for example) to the output (loud speaker). You may add some additional block like an equalizer between pre-amplifier and tone control, or add a crossover between power amplifier anf loudspeaker.

Notes:

• 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.

This is an important action when checking the circuit performance for analysis or when you repair a circuit/electronic device.

When testing circuits you often need to find the voltages at various points, for example the voltage at pin 2 of a 555 timer chip. This can seem confusing – where should you connect the second multimeter lead?

Measuring voltage at a point

• Connect the black (negative -) lead to 0V, normally the negative terminal of the battery or power supply.
• Connect the red (positive +) lead to the point you where you need to measure the voltage.
• The black lead can be left permanently connected to 0V while you use the red lead as a probe to measure voltages at various points.
• You may wish to fit a crocodile clip to the black lead of your multimeter to hold it in place while doing testing like this.

The following is a general block diagram of a radio receiver:

Notes:

• 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.