* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Lab3- BJT-Simulation - Department of Applied Engineering
Invention of the integrated circuit wikipedia , lookup
Surge protector wikipedia , lookup
Oscilloscope wikipedia , lookup
Power electronics wikipedia , lookup
Integrated circuit wikipedia , lookup
Index of electronics articles wikipedia , lookup
Valve RF amplifier wikipedia , lookup
Thermal runaway wikipedia , lookup
Resistive opto-isolator wikipedia , lookup
Schmitt trigger wikipedia , lookup
Molecular scale electronics wikipedia , lookup
Nanofluidic circuitry wikipedia , lookup
RLC circuit wikipedia , lookup
Switched-mode power supply wikipedia , lookup
Regenerative circuit wikipedia , lookup
Opto-isolator wikipedia , lookup
Oscilloscope history wikipedia , lookup
Current source wikipedia , lookup
Operational amplifier wikipedia , lookup
Wilson current mirror wikipedia , lookup
Transistor–transistor logic wikipedia , lookup
Rectiverter wikipedia , lookup
Two-port network wikipedia , lookup
California University of Pennsylvania Department of Applied Engineering & Technology Electrical / Computer Engineering Technology EET 215: Introduction to Instrumentations Lab No.3 Bipolar Junction Transistor (BJT) Multisim Simulation Due Date: 9/21/2015 Names: 1. 2. 3. Signature: Date Bipolar Junction Transistor Objective of the Experiment The main objective of this experiment is to understand the basic functions of the bipolar junction transistor Learning Outcomes Students will demonstrate: - the ability to understand the BJT current gain the ability to calculate transistor voltages and currents understanding of the operation of BJT in saturation and cut-off (as a switch) Understanding and analyzing a DC sweep example Instructions - Read all steps - Answer all questions. Type your answers and make sure they are clear and to the pint. Introduction A BJT transistor is a 3-terminal semiconductor device used in amplification or switching applications. A transistor is referred to by the letter Q. Figure -1: BJT terminals And the electronic symbol is shown along with the current directions. Figure -2: BJT Electronic symbol with current directions. Background Information - With choosing the base as the input side, the collector current, IC, is calculated as a function of the base current, IB, and the transistor’s current gain, β (Beta). IC = β IB It is noticed from the schematic of Figure -2 that IE = IB + IC Substituting the relationship IC = β IB in to the equation IE = IB + IC , we get: IE = IB + IC = IB + β IB = (β+1)IB A- DC Sweep Analysis A well-known method of understanding the operation of a transistor circuit is to investigate the output and how it responds to a specified input. For the NPN BJT transistor, one typically wishes to examine how the output (the collector current) behaves when the collector to emitter voltage (VCE) sweeps between two specified values while the base current is fixed to a pre-specified value. A -1 DC Sweep Analysis: Single Source Sweep. In this case, the base current is fixed at 1uA while the voltage VCE sweeps between 0 to 1 V in increments of 0.01 Volts. Steps: 1- Start Multisim and place an NPN transistor (2N2222) and a current and voltage sources as shown. Q1 2N2222A I1 1uA 2- Set-up the DC sweep as follows: * on the menu bar, click on Simulate>>Analysis>>DC Sweep * Set up the analysis parameters as shown V1 12V * click on the output tab and click onI(QA1(IC)) on the left and then click Add to select it as an output variable * Click on Simulate. You should see a plot of Ic vs. VCE as shown Place your results here as follows: The circuit: The DC Sweep Questions: 1- From the DC sweep, approximately at what VCE value does the collector current start to rise? VCE = Volts 2- The maximum value of Ic is ? 3- This maximum collector current is called the Saturation current or the cut-off current (highlioght the correct answer) A -2 DC Sweep Analysis: Nested Source Sweep. The analysis of A-1 were for a fixed value of base current (IB) One may be interested in investigating a family of curves of Ic vs. VCE for different values of IB Thus, we will have to add to the DC sweep analysis another source that will sweep between 1uA to 8uA in steps of 1uA. This will give us a family of 8 curves. Steps: * in Multisim for the same circuit: Simulate>>Analysis>>DC sweep * Set up the parameters as shown: * Click Simulate. you should obtain a curve as shown: Results: Place your family of curves below Questions: 1- What are the minimum and maximum saturation current (IC sat) and what are the corresponding base currents: Use proper units and prefixes. IC (sat) 2- In all cases, the value of VCE at which the collector currents begin to rise is: IB Volts B- Transistor as a switch When the transistor is operating as a switch, then we have two modes: - Saturation: o Ic = Ic(sat) -- Saturation (maximum) current allowed by the circuit o VCE = VCE(sat.) = 0.2V (almost 0 V) o Thus, one can assume that the switch between the collector and the emitter is closed (0V across the switch.) C E - Cut-off: o IC = IB = IE = 0 A No current is flowing. o The switch acts like and open circuit between the collector and the emitter. C E 1Using Multisim, construct the circuit shown. Here, the transistor is used as a switch. The 330Ω resistor is used for current limiting. Also, notice the LED across the C-E of the transistor. Note, although the circuit shows 2N3904 transistor, you may use the 2N3904 or the 2N2222A that you used in part A. 5V VCC 330Ω 5V 2 VCC 3 1 2N3904 10kΩ 0 Input 0 0 Fig -3: Transistor switch demonstration Place your circuit here: 2- Test your circuit and complete the table below. Vin (Volt) Input Side Q (Saturation or Cut-Off) Sat. or OFF ? LED (ON or OFF)? 0V (LOW) +5V (High) 3Clearly explain your results of the table above. Why is the LED ON and why is it OFF whenever the input is high or low ? C- Q operating in active region. When the transistor is operating in between the saturation and cut-off, it is said that the transistor is in ACTIVE region of operation. Here, the collector current is proportional to the base current according to the equation: Ic = β IB ` Also, IE = IB + IC = IB + β IB = (β+1)IB Then, ohm’s law apply to circuit calculations. 1- Determine the current gain, β, for the transistor as follows: aUsing Multisim, construct the circuit shown in Figure -4 Use the Multisim DMM measure and record the values listed in the table below. (make sure to use popper units) Note: Use the random figure (Figure –x) to help with how the measurements are taken. Figure -4: Transistor in active region of operation Figure –x: Random circuit as an aide for measurements. Parameter Value VRB VRC VBE VCE VBE b- Calculate the base, collector, and emitter currents. Using Ohm’s law, calculate IB, IC IB = VRB/ RB IC = VRC/RC and IE = IC + IB List your results accurately in the table below (use the prefix mA or uA appropriately) Parameter Value IB IC IE c- Determine the current gain, β. β = IC/ IB β = ? d- For reasons that will be apparent later, from the table above, write down the measured value of VBE VBE = e- Repeat and complete the measurements for the table below for RC = 1KΩ and RC = 2.2 KΩ. Table 1: Beta calculations VRB (measured) IB = VRB/RB VCE(measured) RC 1KΩ 2.2KΩ VRC(measured) IC = VRC/RC β= IC/IB 5- Calculate the average value of β as the actual value to be used in calculations Βaverage = -------------------- 6- Did VRB or IB change as RC was changed ? Why or Why not ? 7- Using IB of Table -2 above and the average value of β, theoretically predict the value of VRC and VCE for different values of RC Place your results in table -3 below. Helpful Equations: VRC = Ic Rc VCE = Vcc – VRC = 12V - VRC Table 2: Theoretical Results RC 500Ω 1.6KΩ 10KΩ (!!) VRC (Volts) VCE (Volts) Circuit simulations In Multisim, change RC to the values in the Table and record your measurements in Table 3-B. Table 3-B: Simulation Results RC 500Ω 1.6KΩ 10KΩ (!!) VRC (Volts) VCE (Volts) 9- For which values of Rc did the theoretical and simulated results almost aagree? 10- For which case of Rc did the simulated and theoretical results did not agree? Why? 9- Explain the result for the measurement of VRC and VCE in Table -3. Challenges AFor the circuit of Figure 4 above, what is the maximum value of Rc for the transistor to just reach saturation (VCE = 0.2 V) RC(max.) = ? B- Suppose Rc = 5KΩ, what is the minimum value of RB so that the transistor is operating in linear region (active region)? RB(min) = ?