Laboratory #4 Diode Basics and Applications (II)

Transcription

1 Revised date: 7/2/217 僅供成功大學電機系教學使用, 請勿擅自修改 重製或出版 Laboratory #4 iode Basics and Applications (II) I. Objectives 1. Understand the Zener shunt regulator circuit. 2. Understand the operational principles of clipping and clamping circuits. II. Components and Instruments 1. Components (1) Zener diode 1 (2) iode (IN44) 1 (3) Resistor : 47kΩ 1, 1kΩ 1, 4.7kΩ 1, 2.2kΩ 1, 1.5kΩ 1, 1kΩ 1, 47Ω 1 (4) Capacitor :.1μF 1 2. Instruments (1) Function generator (2) C power supply (3) igital multimeter (4) Oscilloscope III. Reading Concentration will be on Section 3.4 and 3.6 of the Textbook Microelectronic Circuits Sixth Edition. IV. Preparation 1. Zener shunt regulator (1) Specifying and modeling the Zener diode The i-v curve is shown in Fig. 4.1 that the diode exhibits in the breakdown region and the almost-constant voltage drop that this indicates suggest that diodes operating in the break-down region can be used in the design of voltage regulators. This is an important application of diodes operating in the reverse breakdown region, and special diodes are manufactured to operate specifically in the breakdown region. Such diode are called Zener diodes. Prof. Tai-Haur Kuo, EE, NCKU, Tainan City, Taiwan 4-1 郭泰豪, 成大電機,Electronics Laboratory (1)

2 Revised date: 7/2/217 僅供成功大學電機系教學使用, 請勿擅自修改 重製或出版 Fig. 4.1 iode i-v characteristics The almost-linear i-v characteristic of the Zener diode suggests that the device can be modeled as indicated in Fig Fig. 4.2 Model for the Zener diode (2) Zener shunt regulator circuit The Zener shunt circuit is shown in Fig. 4.3, the use of Zener diodes in the design of shunt regulators, so named because the regulator circuit appears in parallel (shunt) with load. R S + Z - Fig. 4.3 Zener shunt regulator circuit Prof. Tai-Haur Kuo, EE, NCKU, Tainan City, Taiwan 4-2 郭泰豪, 成大電機,Electronics Laboratory (1)

3 Revised date: 7/2/217 僅供成功大學電機系教學使用, 請勿擅自修改 重製或出版 There are two parameters to evaluate the regulation function: line regulation and load regulation. In Fig. 4.3, we can use the model in Fig. 4.2 to derive the equation (1) as following: R S rz rz V = + out VZ Vin I L (1) The line regulation is defined as equation (2): Vout rz Line regulation = = (2) V R + r in S Line regulation is a measure of the ability of the power supply to maintain its output voltage given changes in the input line voltage. Line regulation is expressed as percent of change in the output voltage relative to the change in the input line voltage. The load regulation is defined as equation (3): Z Load regulation V = I out L rz = + r Z (3) Load regulation is a measure of the ability of an output channel to remain constant given changes in the load. 2. Clipping circuits Clipping circuits are also called clipper or limiters. Limiters find application in a variety of signal processing systems. One of their applications is in limiting the voltage between the two input terminals of an opamp to a value lower than the breakdown voltage of the transistors that make up the input stage of the opamp circuit. iodes can be combined with resistors to provide simple realizations of the limiter function. A number of examples are depicted in Fig. 4.4 to Fig In each part of the figure both the circuit and its transfer characteristics are given. And in these examples, we assume that the diodes are ideal for simplification. Prof. Tai-Haur Kuo, EE, NCKU, Tainan City, Taiwan 4-3 郭泰豪, 成大電機,Electronics Laboratory (1)

4 Revised date: 7/2/217 僅供成功大學電機系教學使用, 請勿擅自修改 重製或出版 Fig. 4.4 The output having series connection of diode 1 2 V V Fig. 4.5 The output having series connection of diode 2 2 V V Fig. 4.6 The output having series connection of diode 3 Prof. Tai-Haur Kuo, EE, NCKU, Tainan City, Taiwan 4-4 郭泰豪, 成大電機,Electronics Laboratory (1)

5 Revised date: 7/2/217 僅供成功大學電機系教學使用, 請勿擅自修改 重製或出版 R S Fig. 4.7 The output having parallel connection of diode 1 ( << RL) R S +2 V 2 V + - Fig. 4.8 The output having parallel connection of diode 2 ( << RL) R S 2 V V Fig. 4.9 The output having parallel connection of diode 3 ( << RL) Prof. Tai-Haur Kuo, EE, NCKU, Tainan City, Taiwan 4-5 郭泰豪, 成大電機,Electronics Laboratory (1)

6 Revised date: 7/2/217 僅供成功大學電機系教學使用, 請勿擅自修改 重製或出版 3. Clamping circuits Clamping circuits are used to shift signal dc level without changing the shape of waveform. The circuits are also called dc restorers. A number of examples are depicted in Fig. 4.1 to Fig In each part of the figure both the circuit and its transfer characteristics are given. C +1 V V Fig. 4.1 The clamping circuit 1 C 2 V V -8 V Fig The clamping circuit 2 C 2 V V +2 V Fig The clamping circuit 3 Prof. Tai-Haur Kuo, EE, NCKU, Tainan City, Taiwan 4-6 郭泰豪, 成大電機,Electronics Laboratory (1)

7 Revised date: 7/2/217 僅供成功大學電機系教學使用, 請勿擅自修改 重製或出版 V. Explorations 1. Zener shunt regulator circuit Connect the circuit as shown in Fig and use your MM to measure the dc voltage of Vout, and the current (IZ) through the Zener diode. Please finish the Table 4.1 and Table 4.2. R S + 1.5k Ω Z I Z I L - 6.2V Fig Table 4.1 (RL = 1 KΩ) Vin (V) Vout (V) IZ (ma) Table 4.2 (Vin = 12 V) RL (Ω) 1 k 4.7 k 2.2 k 1 k 47 Vout (V) IL (ma) 2. Clipping circuits Connect the circuit as shown in Fig. 4.4 to Fig. 4.9, and use the oscilloscope to measure the waveforms of Vout. The input voltage (Vin) is a 1Vpp and 1kHz sine wave, and the value of is 47 Ω and RL is 47 kω. The diode can be the 1N4X series. 3. Clamping circuits Connect the circuit as shown in Fig. 4.1 to Fig. 4.12, and use the oscilloscope to measure the waveforms of Vout. The input voltage (Vin) is a 1Vpp and 1kHz square wave, and the value of C is.1μf. The diode can be the 1N4X series. Prof. Tai-Haur Kuo, EE, NCKU, Tainan City, Taiwan 4-7 郭泰豪, 成大電機,Electronics Laboratory (1)

8 Revised date: 7/2/217 僅供成功大學電機系教學使用, 請勿擅自修改 重製或出版 Class: Name: Laboratory #4 Pre-lab Student I: Note: In these simulations, the diode can be the 1N4X series. 1. Connect the circuit as shown in Fig and simulate the circuits by PSpice. Show the output (Vout) waveform which is across the load resistor. Set the Vin to 12 V, and set the value of RL to1 kω. And select the Zener diode (1n75). Please attach the schematic and simulation results. 2. Connect the circuit as shown in Fig. 4.4 to Fig. 4.9 and simulate the circuits by PSpice. The input voltage (Vin) is a 1Vpp and 1kHz sine wave, and the value of is 47 Ω and RL is 47 kω. Show the output (Vout) waveform. Please attach the schematic and simulation results. 3. Connect the circuit as shown in Fig. 4.1 and Fig and simulate the circuits by PSpice. The input voltage (Vin) is a 1Vpp and 1kHz square wave, and the value of C is.1μf. Show the output (Vout) waveform. Please attach the schematic and simulation results. Prof. Tai-Haur Kuo, EE, NCKU, Tainan City, Taiwan 4-8 郭泰豪, 成大電機,Electronics Laboratory (1)

9 Revised date: 7/2/217 僅供成功大學電機系教學使用, 請勿擅自修改 重製或出版 Class: Name: Laboratory #4 Report Student I: Exploration 1 Table 4.1 Vin (V) Vout (V) IZ (ma) Table 4.2 RL (Ω) 1 k 4.7 k 2.2 k 1 k 47 Vout (V) IL (ma) Exploration 2 Output waveforms: Exploration 3 Output waveforms: Problem 1 Please derive the equation (1) from Fig 4.3. R S rz rz V = + out VZ Vin I L (1) Problem 2 What is the regulation function which we test in the Table 4.2? (line regulation or load regulation) And please make a short description of it. Problem 3 Observe the experiment results from Fig. 4.7 to Fig. 4.9, and what is the limitation of the clipping circuits? (Hint: the relation of RL and ) Prof. Tai-Haur Kuo, EE, NCKU, Tainan City, Taiwan 4-9 郭泰豪, 成大電機,Electronics Laboratory (1)

10 Revised date: 7/2/217 僅供成功大學電機系教學使用, 請勿擅自修改 重製或出版 Problem 4 Given 47 kω resistor and a sine wave input with 1Vpp amplitude and 1 khz frequency. Please design a clipper to generate the output waveform shown in Fig V -2 V Fig Conclusion Prof. Tai-Haur Kuo, EE, NCKU, Tainan City, Taiwan 4-1 郭泰豪, 成大電機,Electronics Laboratory (1)