Imianorthosi
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3.7 Applications of diodes
The applications of diodes (transistors) are many.
Used as in analog electronics circuits like rectifiers, ie as controlled switches for crossing <no electricity (imianorthosi, full recovery) and digital electronic circuits for producing pulse signals (clippers). Also used in radio and TV to select the transmit frequency (variable capacity diodes) and raising the voltage (voltage multiplier).
Previously diodes manufactured only in discrete form as shown in Figure (3.7.1) where the shape and size depends on their characteristics (voltage, current, power, etc.) With the development of electronic technology, especially after 1970, the diodes are manufactured in the form of integrated circuit (IC) containing 2, 4 or 8 channels or disconnected, or in connection common anode or common cathode or bridge.
These provisions are called diodes factions <tables diode (diode arrays). Figure (3.7.2) seem diodes or bridge layout and OK
Figure 3.7.2.
Provisions diode (a) Bridge, (b) CA3141 (RCA)
Figure 3.7.1.
Diodes in discrete form
16 15 14 13 12 11 10 7
(B)
1 2 3 4 5 6 7
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3.7.1 Imianorthosi
The circuits used in the preceding paragraphs of capital, the input voltage source dc voltage source was which remains constant with time. Voltage using almost all electronic devices.
The power plants produce AC voltage, the value of which does not remain constant over time but varies. The alternating voltage has significant advantages over the continuum, especially in the transfer process from manufacturing plants to centers of consumption and is widely used.
They therefore need electronic devices that will convert alternating current into constant. These provisions are called feeders and will be studied in the second grade. The power supplies contain between other electronic components and so-called rectifiers.
The rectifiers or rectifier devices exhibit little resistance when polarized in good time and great resistance when polarized in reverse time. Previously rectifiers were used as chemical elements or compounds such as selenium, germanium, copper oxide, etc. Now mainly used as PN diodes contact resistance reverse direction is very much greater than the resistance proper direction. (RR / RF = 10.000 -1.000.000)
The simplest rectifier circuit shown in Figure (3.7.3). As we see, consists of alternating voltage source V 'sinusoidal with a maximum value (amplitude Vm), frequency f, time
Figure 3.7.3. Simple rectifier circuit or imianorthosis
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KPYITAMOAIOAOI
T and angular frequency omega = 2pi, an ideal diode D (Vy = 0, RD = 0) and a load resistor RL.
The circuit is called simple rectifier circuit imianorthosis and the output voltage VL is said imianorthomeni trend.
When the input voltage has a positive value, ie when 0 <V <Vm and 0 <t <T / 2 the diode is biased at the proper time and thus conduct. Because the diode is ideal there is no voltage drop at the edges and so all the input voltage is transferred to the output. Figure 3.7.4 (a) shows the waveforms of voltage and current output.
When the input voltage is negative, ie-Vm <V | <0 and the T-miperiodo / 2 <t <T, the diode is reverse biased and does not conduct
Figure 3.7.4. Voltages and currents at imianorthosi (a) Positive input voltage (b) Negative input voltage
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when the circuit is open and the current flowing through the load is zero and hence the output voltage is reset as shown in Figure 3.7.4 (b). The same happens at the second (T <t <2T), third (2T <t <3T), etc. time.
From the above analysis we found that voltage and output current only during the half-positive polarity of the input voltage and therefore the output voltage is half that imianorthomeni - bristled.
When the diode is not ideal it is recognized as a knee voltage Vg and a good wear resistance RF ^ 0. In this case the maximum output current will be:
and the maximum output voltage:
As is known, a constant current measured by ammeter dc current (dc), while an alternating current is measured by an ammeter for alternating (ac). The direct current imianorthomeno presents two different values when measured with instruments with DC and AC This is because it contains continuous and alternating current component. The same applies to the imianorthomeni trend. The constant (dc) component of imianorthomenou power is defined as the average price of imianorthomenou power throughout the period 0 <t <T. With mathematical calculations is that the value of this component are:
'Dc = pi »0,318 Im 3.7.3> Vm where Im = 3.1415 and p = ... The constant (dc) component of the voltage measuring a dc voltmeter are:
KPYITAMOAIOAOI
Vdc = q »0,318 Vm =-mR, 3.7.4 The effective (rms) value of current and voltage, the sizes measured with an AC ammeter and voltmeter, respectively, given by the relation: Im Vm
3.7.5
Example 3.7.1
For the circuit given in Figure 3.7.3: Maximum (peak) ac voltage source Vm = 50 V, load resistance RL = 100 O, V = 0,7 V, RF = 50 W. To determine the constant voltage load the DC load and the effective value of current imianorthomenou.
Solution
From the relation (3.7.1) we have:
Vm - V 50-0,7 49,3 _ 4 I = 329 mA Im RL + RF 100 + 50 150 329mA
From relations (3.7.3) and (3.7.4) we have:
Idc = 0,318 · Im = 105 mA.
Vdc = Idc RL = 105 mA x 100 Z = 10,5 V.
Finally, relation (3.7.5) gives:
ILrms = y = 3 | 9 = 164,5 mA
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