Exp_5_Diodes_06 - Diodes Page 1 Diodes V-I Characteristics...

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Diodes, Page 1 Diodes V-I Characteristics – signal diode Measure the voltage-current characteristic of a standard signal diode, the 1N914, using the circuit shown below. The purpose of the back-to-back power supplies is to make it easy to make measurements near zero supply voltage. Plot the V-I characteristic on graph paper to show the rapid rise in forward current when the forward voltage approaches 0.7 volts. It should look something like the figure below. Notice that the current in milliamps is given by the voltage across a 1K resistor as measured in volts. Therefore, you can measure V vs. I by connecting a digital voltmeter alternately across the diode and the resistor. Repeat the measurement using the LabView program, I_vs_v using a 1K resistor for the standard. Make a printout of the curve and insert into your lab notebook. It is a good idea to preserve this circuit intact, as it will be used again later in the lab. Temperature dependence Reverse bias the diode with ~-20 V and observe the reverse current (should be about 0.2 μ A). Touch a soldering iron to the metal lead close to the diode and note the percentage change in reverse current. There is a big effect because the minority carriers that transport the reverse current are thermally generated. Now bias the diode in a forward direction to get a forward current of about 0.2 mA. Repeat the heat treatment and observe the change in current. Figure 2: Diode Circuit. 5V Var. 1k V D + - -18V 0 I D (mA) 0.7V V D Figure 1: Diode V-I Plot.
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Diodes, Page 2 The Half-Wave Rectifier The basic half-wave rectifier with resistive load looks like the circuit above. The Input and Output waveforms are shown on the right. The half-wave rectifier with filter capacitor and resistive load is shown in Figure
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Exp_5_Diodes_06 - Diodes Page 1 Diodes V-I Characteristics...

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