Trip 5. Diodes
The fifth trip introduces a fundamental semiconductor component in the world of electrical engineering: the diode. Several types of diodes are described in this Trip: the simple pn junction diode used typically for rectification, the varactor diode which is a voltage controlled variable capacitor, often used for tuning resonant circuits, and the light emitting diode (LED) used as a visual indicator.
Please click to preview the experiments in this Trip: 1, 2, 3, 4, 5, 6, 7.
![1](javascript:ReplaceContentInContainer('content-exp',' <h3>Experiment 1. Half-wave Rectifier</h3>
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<img src="./images/Exp1HalfWaveRectifier.jpg" width=" 333 " align=" right" style=" float:right; padding-right:10px; padding-bottom:5px;">
<p> Many of the electronics one meets in daily life use a DC supply. The half wave rectifier is a primary function necessary to convert AC power from the main power outlet into DC power. The half-wave rectification is a process through which using a diode a sine wave is clipped at the bottom. Basically the half-wave rectifier cuts half of the sine wave generating a positive only wave. This way, from a sine wave with zero DC average, the half wave rectifier creates a wave with positive DC average.
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<p> The <b>Topnotch Meter</b> is used to display such a rectified half wave as shown in the image on the right.
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![2](javascript:ReplaceContentInContainer('content-exp',' <h3>Experiment 2. Half-wave Peak Rectifier</h3>
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<img src="./images/Exp2HalfWavePeakRectifier.jpg" width=" 333 " align=" right" style=" float:right; padding-right:10px; padding-bottom:5px;">
<p> In Experiment 2, the half wave rectifier, the DC level is less than half the incoming sine wave. In this experiment, the half wave peak rectifier, the DC level extracted is close to be exactly the amplitude of the incoming sine wave. This is accomplished by having the diode connected to an RC circuit. When the diode is on, the RC circuit is charging at the incoming sine wave voltage level minus a constant voltage drop. When the diode is off the capacitor maintains the DC level discharging only a little through the load resistor.
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<p> The <b>Topnotch Meter</b> is used to capture this phenomenon. A rippled DC line should be seen on the screen of the meter.
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![3,](javascript:ReplaceContentInContainer('content-exp',' <h3>Experiment 3. Limiter</h3>
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<img src="./images/Exp3Limiter2.jpg" width=" 333 " align=" right" style=" float:right; padding-right:10px; padding-bottom:5px;">
<p> Many of the common electronic devices encountered in daily life need to ensure certain voltages are confined within a certain range. For example an amplifier might need to ensure that its inputs are not going too far outside the power supply rails to avoid over-voltage problems.
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<p> The limiter circuit described in this experiment takes a voltage as an input and if it is greater than a certain limit-value outputs that certain limit-value. By doing so it limits the signal.</p>
<p> The limiter circuit relies on the fact that when the diode is turned on by a high voltage it becomes a constant voltage drop, low resistance circuit. The <b>Topnotch Meter</b> is used to verify the limiter circuit behaviour.
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Experiment 1. Half-wave Rectifier
Many of the electronics one meets in daily life use a DC supply. The half wave rectifier is a primary function necessary to convert AC power from the main power outlet into DC power. The half-wave rectification is a process through which using a diode a sine wave is clipped at the bottom. Basically the half-wave rectifier cuts half of the sine wave generating a positive only wave. This way, from a sine wave with zero DC average, the half wave rectifier creates a wave with positive DC average.
The Topnotch Meter is used to display such a rectified half wave as shown in the image on the right.