Lab 4 - 2B 2010

Lab 4 2B 2010 - 1 © Bob York ECE 2B Lab#4 Lab 4 Transistor Switching Circuits Overview This lab continues our exploration of basic transistor

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Unformatted text preview: 1 © Bob York ECE 2B Lab #4 Lab 4 Transistor Switching Circuits Overview This lab continues our exploration of basic transistor switching circuits. We will examine some considerations for driving capacitive and inductive loads, and put this to use in creating a simple DC fan driver and DC-DC Boost converter. In the process we will apply and observe much of what you have learned in about 1 st and 2 nd-order circuit responses. Table of Contents Pre-lab Preparation 2 Before Coming to the Lab 2 Parts List 2 Background information 3 Constant-Current Charging of Capacitors 3 Measuring Rise-Time in Switching Waveforms 3 Switching Response of RLC Load 4 In-Lab Procedure 6 4.1 Driving Capacitive Loads 6 BJT Inverter 6 CMOS Inverter (Optional, for Extra Credit) 7 4.2 Inductive Loads 8 Ringing Response 8 Inductive Spiking and Diode Clamp 8 Motor Driver Circuit 9 4.3 DC-DC “Boost” Converter 10 2 Transistor Switching Circuits © Bob York 2 Pre-lab Preparation Before Coming to the Lab □ Read through the lab experiment to familiarize yourself with the components and assembly sequence. □ Calculate the drain resistor that achieves critical damping on the leading edge (on-off transition) for the circuit in Figure 4-8. The information provided in the background section may help. □ Each group should obtain a parts kit from the ECE Shop. Parts List The ECE2 lab is stocked with resistors so do not be alarmed if you kits does not include the resistors listed below. Some of these parts may also have been provided in an earlier kit. Laboratory #4 Transistor Switching Circuits Qty Description 2 2N7000 NMOS 1 2N3904 NPN BJT 1 2N3906 PNP BJT 1 CD4007 CMOS pair/inverter 2 1N4005 diode rectifier 1 12V DC brushless fan, 1.6 in. (40mm), 100mA 1 2in strip of double-sided foam tape 4 0.1uF capacitor (CKO5 low-volt. Ceramic) 1 10uF capacitor (electrolytic, 25V, radial) 1 100uH toroidal inductor (vertical) 2 10-Ohm 1/4 Watt resistor 1 22-Ohm 1/4 Watt resistor 1 100-Ohm 1/4 Watt resistor 1 470-Ohm 1/4 Watt resistor 1 1-KOhm 1/4 Watt resistor 1 3.3-KOhm 1/4 Watt resistor 3 10-KOhm 1/4 Watt resistor 2 100-KOhm 1/4 Watt resistor Background information 3 © Bob York 3 Background information Suggested reading to complement this section: ■ Basics on FET and BJT switches from lectures or text (e.g. Neamen 3.3, 5.3, or Sedra & Smith 4.4-4.5, 5.3-5.5) and posted notes. ■ Other posted material on DC-DC switching converters Constant-Current Charging of Capacitors In our study of 1 st-order RC circuits the capacitors were always charged/discharged through a resistor as in the circuit of Figure 4-1a. If the battery voltage DD V is applied at t , the capacitor voltage is given by the familiar exponential dependence / ( ) 1 out DD t RC V t V e (4.1) Initially (for small t ) the capacitor voltage increases linearly, but then the charging rate slows and the capacitor voltage approaches its final steady-state value asymptotically. This is because the charge transfer to the...
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This note was uploaded on 03/17/2010 for the course ECE 2B taught by Professor York during the Winter '07 term at UCSB.

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Lab 4 2B 2010 - 1 © Bob York ECE 2B Lab#4 Lab 4 Transistor Switching Circuits Overview This lab continues our exploration of basic transistor

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