4.1 the ideal diode
4.1.1 Current–Voltage Characteristic
The ideal diode may be considered to be the most fundamental nonlinear circuit element. It
is a two-terminal device having the circuit symbol of Fig. 4.1(a) and the i–v characteristic
shown in Fig. 4.1(b). The terminal characteristic of the ideal diode can be interpreted as follows: If a negative voltage (relative to the reference direction indicated in Fig. 4.1a) is
applied to the diode, no current flows and the diode behaves as an open circuit (Fig. 4.1c).
Diodes operated in this mode are said to be reverse biased, or operated in the reverse direction. An ideal diode has zero current when operated in the reverse direction and is said to be
cut off, or simply off.
On the other hand, if a positive current (relative to the reference direction indicated in Fig.
4.1a) is applied to the ideal diode, zero voltage drop appears across the diode. In other words,
the ideal diode behaves as a short circuit in the forward direction (Fig. 4.1d); it passes any current with zero voltage drop. A forward-biased diode is said to be turned on, or simply on.
From the above description it should be noted that the external circuit must be designed to
limit the forward current through a conducting diode, and the reverse voltage across a cutoff
diode, to predetermined values. Figure 4.2 shows two diode circuits that illustrate this point. In
the circuit of Fig. 4.2(a) the diode is obviously conducting. Thus its voltage drop will be zero, and
the current through it will be determined by the +10-V supply and the 1-kΩ resistor as 10 mA.
The diode in the circuit of Fig. 4.2(b) is obviously cut off, and thus its current will be zero, which
in turn means that the entire 10-V supply will appear as reverse bias across the diode.
The positive terminal of the diode is called the anode and the negative terminal the
cathode, a carryover from the days of vacuum-tube diodes. The i–v characteristic of the
ideal diode (conducting in one direction and not in the other) should explain the choice of its
arrow like circuit symbol.
As should be evident from the preceding description, the i–v characteristic of the ideal
diode is highly nonlinear; although it consists of two straight-line segments, they are at 90° to
one another. A nonlinear curve that consists of straight-line segments is said to be piecewise
linear. If a device having a piecewise-linear characteristic is used in a particular application
in such a way that the signal across its terminals swings along only one of the linear
4.1 the ideal diode4.1.1 Current–Voltage CharacteristicThe ideal diode may be considered to be the most fundamental nonlinear circuit element. Itis a two-terminal device having the circuit symbol of Fig. 4.1(a) and the i–v characteristicshown in Fig. 4.1(b). The terminal characteristic of the ideal diode can be interpreted as follows: If a negative voltage (relative to the reference direction indicated in Fig. 4.1a) isapplied to the diode, no current flows and the diode behaves as an open circuit (Fig. 4.1c).Diodes operated in this mode are said to be reverse biased, or operated in the reverse direction. An ideal diode has zero current when operated in the reverse direction and is said to becut off, or simply off.On the other hand, if a positive current (relative to the reference direction indicated in Fig.4.1a) is applied to the ideal diode, zero voltage drop appears across the diode. In other words,the ideal diode behaves as a short circuit in the forward direction (Fig. 4.1d); it passes any current with zero voltage drop. A forward-biased diode is said to be turned on, or simply on.From the above description it should be noted that the external circuit must be designed tolimit the forward current through a conducting diode, and the reverse voltage across a cutoffdiode, to predetermined values. Figure 4.2 shows two diode circuits that illustrate this point. Inthe circuit of Fig. 4.2(a) the diode is obviously conducting. Thus its voltage drop will be zero, andปัจจุบันผ่านมันจะถูกกำหนด โดยการ + 10-จัดหา V และตัวต้านทาน 1 k ω 10 mAไดโอดในวงจรของ Fig. 4.2(b) ถูกตัดออกอย่างชัดเจน และดัง นั้นปัจจุบันจะศูนย์ ที่จะหมายความว่าจ่าย 10 V ทั้งหมดจะปรากฏเป็น ย้อนความโน้มเอียงในไดโอดเทอร์มินัลบวกของไดโอดคือขั้วบวกและลบเทอร์มินัลแคโทด carryover จากวันของไดโอดได้หลอดสุญญากาศ I-v ลักษณะของการไดโอดที่เหมาะ (ทำ ในทิศทางหนึ่ง และไม่อยู่ ในอื่น ๆ) ควรอธิบายตัวเลือกของลูกศรเช่นสัญลักษณ์วงจรควรจะเห็นได้จากคำอธิบายก่อนหน้านี้ i-v ลักษณะของพักไดโอดจะสูงไม่เชิงเส้น แม้ว่าประกอบด้วยสองส่วนที่เส้นตรง อยู่ที่ 90 องศาให้อีกแบบหนึ่ง กล่าวว่า จะ piecewise โค้งไม่เชิงเส้นที่ประกอบด้วยส่วนของเส้นตรงเชิงเส้น ถ้ามีใช้อุปกรณ์ที่มีลักษณะเชิง piecewise ในโปรแกรมประยุกต์เฉพาะในลักษณะว่า สัญญาณผ่านเทอร์มินัลของชิงช้าตามหนึ่งเชิงเส้น
การแปล กรุณารอสักครู่..
