KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Diode Circuit 1 2 KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK IC voltage regulator RC filtering LC filtering 3 IC voltage regulator KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK voltage-regulator filtering (integrated circuit (IC)) three-terminal voltage regulator 4 KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK IC voltage regulator 5 Diode Circuit KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Clippers circuit: Positive clipper • Rectifier Diodes: Low frequencies (60Hz)>>1N4001 • Small-Signal Diodes: less than 0.5 W>>1N914 6 Diode Circuit KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Clippers circuit: Defining Conditions 1N914 7 KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Diode Circuit Clippers circuit: Negative clipper 8 Diode Circuit KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Clippers circuit: Negative clipper - polarity protection circuit 9 Diode Circuit KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK The Limiter or Diode Clamp “a positive-negative limiter to protect its input” • op amp • The typical input voltage to an op amp is less than 15 mV. • an IC • moving-coil meter 10 Diode Circuit KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Biased Clippers Biased positive clipper biased negative clipper 11 Diode Circuit KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Variations Clipper using three-diode off set 12 Diode Circuit KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Variations voltage divider biases clipper 13 Diode Circuit KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Variations voltage divider biases clipper 14 KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Ex. Suppose that the output clipper requirement is 5.7 V. With the Vdc is 12V, calculate the R1 and R2 15 Diode Circuit KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Variations diode clamp protects above 5.7 V 16 KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Positive Clamper 17 KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Positive Clamper เวลาของ RLC ต้องมากกว่าเวลาของ สัญญาณขาเข้า ดังนัน้ จึงใช้กฏ มากกว่า 100 เท่า จะได้ว่า พิจารณาสัญญาณไฟลบ ไดโอดทางาน (ปิ ดวงจร) ทาให้ทาตัวเก็บประจุเก็บ ประจุได้เท่ากับ Vp พิจารณาสัญญาณไฟบวก และในชั่วขณะตัวเก็บ ประจุเสมือนเป็ นแบตเตอรีแ่ รงดัน Vp ไดโอดไม่ ทางานทางาน (เปิ ดวงจร) ทาให้แรงดันนีไ้ ปช่วย ยกระดับของสัญญาษ 18 KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Positive Clamper 19 KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Negative Clamper 20 KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Peak-to-Peak Detector 21 Voltage Multipliers KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Voltage doubler Peak-to-Peak Detector 22 Voltage Multipliers KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Voltage doubler Why we using a voltage doubler when we can change the turns ratio to get more output voltage? 23 KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Voltage Tripler 24 KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK QUADRUPLER OUTPUT 25 KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Assignment 1 Sketch the output waveform. What is the maximum positive voltage? The maximum negative? 1.1 1.2 26 The diode clamp protects the sensitive circuit. What are the limiting levels? KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Assignment 2 27 What is maximum positive output voltage? Maximum negative output voltage? Sketch the output waveform. KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Assignment 3 28 Sketch the output waveform. What is the maximum positive voltage? The maximum negative? KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Assignment 4 29 Sketch the output waveform of the clamper and final output. What is the dc output voltage with ideal diodes? To a second approximation? KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Assignment 5 30 Calculate the dc output voltage in Figure. KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Assignment 6 31 Special-Purpose Diodes KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK The Zener Diode (particular test current) (the maximum reverse current) 32 Special-Purpose Diodes KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Ideal Zener Diode Ohm’s Law • • 𝑉𝑠 − 𝑉𝑧 𝐼𝑠 = 𝑅𝑠 To get breakdown operation, the source voltage VS must be greater than the zener breakdown voltage VZ A series resistor R is always used to limit the zener current to less than its maximum current rating. Otherwise, the zener diode will burn out, like any device with too much power dissipation. S 33 Special-Purpose Diodes KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Zener Regulator Suppose the zener diode of Figure has a breakdown voltage of 10 V. What are the minimum and maximum zener currents? 34 Zener Regulator KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK The Loaded Zener Regulator Breakdown Operation 35 Zener Regulator KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Zener Regulator Breakdown Operation Is the zener diode of Fig. operating in the breakdown region? What does the zener current equal in Fig 36 Special-Purpose Diodes KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Zener Regulator Preregulator. What does the circuit do? 37 Special-Purpose Diodes KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Zener Regulator What does the circuit do? 38 Assignment 7 1. KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK 2. 3. 4. 5. If the zener diode is disconnected in Figure, what is the load voltage? Calculate all three currents in Figure Assuming a tolerance of 65 percent in both resistors of Figure, what is the maximum zener current? Suppose the supply voltage of Figure can vary from 24 to 40 V. What is the maximum Zener current? The zener diode of Figure is replaced with a 1N4742A. What are the load voltage and the Zener current? 39 KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Special-Purpose Diodes Light-Emitting Diodes (LEDs) LED Voltage and Current the typical voltage drop is from 1.5 to 2.5 V for currents between 10 and 50 mA 40 Break down voltage 3-5V Special-Purpose Diodes KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Light-Emitting Diodes (LEDs) What is the approximate LED current if the dc input voltage is 5 V and the series resistance is 2.2 kΩ? 41 Special-Purpose Diodes KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Light-Emitting Diodes (LEDs) How much LED current is there if the series resistance is 470 Ω? 42 KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Special-Purpose Diodes 43 KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Special-Purpose Diodes Seven-Segment Display 44 KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Special-Purpose Diodes Photodiode Optocoupler 45 Special-Purpose Diodes KING MONGKUT’S UNIVERSITY OF TECHNOLOGY NORTH BANGKOK Schottky diodes The most important application of Schottky diodes is in digital computers. 46 47
