OverviewBackground1. Transistor Junctions2. DC Transistor Curves3. Dynamic Curve Tracer4. DC JFET CurvesPhysics 375, Laboratory 6Transistor PropertiesOverviewThe purpose of these experiments is to measure the current-voltage curves of a bipolar junctiontransistor, and to test the DC properties of transistors.BackgroundA bipolar junction transistor is made from two junctions of a p-type and n-type semiconductor.The 2N3904 is an npn transistor with layers of n-type, p-type and n-type semiconductor. The2N3904 comes in a TO-92 plastic case with leads for emitter, base and collector.The 2N3904 has maximum ratings as follows:VCE<40VVCB<60VVEB<6.0VIC< 200 mAP=ICVCE< 625 mWThe base-emitter junction acts like a diode. However, when a current flows from the base to emit-ter (IB) of the transistor, a current is induced to flow from the collector to emitter (IC) such thatwhere β is a characteristic factor for the transistor. For the 2N3904 β is between 100 and 400.E2N3904BCECBICβIB=PHYS375Lab6,p.2A junction field effect transistor (JFET) is made from a junction of a p-type and n-type semicon-ductor, but the junction is used to control the conductance in one of the semiconductor layers. Inmany ways a JFET behaves like a bipolar junction transistor with the drain, source and gateequivalent to the collector, emitter and base. The 2N5485 is an n-channel JFET and comes in aTO-92 plastic case with leads for drain, source and gate.The 2N5485 has maximum ratings as follows:VDG<25V,-VGS<25VID<30mA,P=IDVDS< 300 mW1. Transistor JunctionsMeasure the resistance across a 1N914 diode in both directions. Measure the resistance betweeneach pair of leads of a 2N3904 transistor and for each polarity of the DMM leads. This should be6 different measurements for the transistor. Compare the pairs to the result from the diode. Doesthe transistor act like two diodes?2. DC Transistor CurvesConnect the variable power supply, an npn transistor (2N3904), resistor, and DMM:Figure 1: DC Transistor MeasurementD2N5485GDSGS100 ΩDMMVcc2N3904VbbRBPHYS375Lab6,p.3Usea1.5VbatteryforVbband the variable power supply for Vcc.UseRB= 470 kΩ,andVcc=0.1V, and measure the voltage drop across RBto get IB. Now measure the voltage across the 100 Ωresistor, VE. Calculate VCEand ICat this value of IB. Repeat the measurement of VEfor Vcc=0.2,0.5, 1, 2, and 5 V, and graph ICvs. VCE. Change RB= 220 kΩ and repeat the measurement of thecurve. Find a third curve by using RB= 100 kΩ. What value can be derived for β for this transis-tor.3. Dynamic Curve TracerReplace the variable power supply in part 2 with a function generator set for triangle waves withan amplitude of 2 V at 1 kHz. Use the Ch1 (X) input of the scope to measure the triangle waveand measure the voltage across the 100 Ω resistor with the Ch2 (Y) input as in Figure 2.Figure 2: Dynamic I-V Curve MeasurementSet the oscilloscope time/div setting to X-Y. The X-axis will now read volts from the ch1 inputand the Y-axis will read volts from the ch2 input. Compare the curve on the oscilloscope with thedata from part 2.100 ΩYVcc2N3904VbbRBXPHYS375Lab6,p.44. DC JFET CurvesConnect two power supplies an n-channel transistor (2N5485), potentiometer, and resistor as infigure 1.Figure 1: DC JFET MeasurementUse a power supply set to 5 V for Vgg(note the inverted polarity) and a 10 kΩ potentiometer asRGto set the voltage at the gate VGS. Use the variable power supply for Vdd.SetVGS=0VandVdd= 0.5 V, and measure VDSwith a DMM. Subtract VDSfrom Vddto get the voltage drop acrossRD, and use that to calculate ID. Repeat the measurement of VDSand IDfor Vdd=1.0,2.0,4.0,6.0, 10.0, and 15.0 V, and graph IDvs. VDS. Find the curve of IDvs. VDSagain for VGS=-0.5V,and -1.0 V. Plot the three curves on a single graph. Plot IDvs. VDSfor the region of constant ID.Calculate gm= ∆ID/