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 university:courses:alm1k:alm-lab-4 [13 Apr 2015 17:27]Doug Mercer created university:courses:alm1k:alm-lab-4 [08 Jan 2018 15:18]Doug Mercer [Questions:] 03 Nov 2021 20:31 Doug Mercer [Activity: BJT Characteristic Curves] 25 Jun 2020 22:07 external edit18 Sep 2019 15:32 Doug Mercer [Activity 4: BJT Characteristic Curves] 18 Sep 2019 15:31 Doug Mercer [Questions:] 03 May 2019 11:53 Antoniu Miclaus [Questions:] 08 Jan 2018 16:06 Doug Mercer add beta vs Vce plot08 Jan 2018 15:18 Doug Mercer [Questions:] 08 Jan 2018 15:11 Doug Mercer [NPN device Directions:] 08 Jan 2018 15:10 Doug Mercer [Background:] 13 Apr 2015 17:27 Doug Mercer created Next revision Previous revision 03 Nov 2021 20:31 Doug Mercer [Activity: BJT Characteristic Curves] 25 Jun 2020 22:07 external edit18 Sep 2019 15:32 Doug Mercer [Activity 4: BJT Characteristic Curves] 18 Sep 2019 15:31 Doug Mercer [Questions:] 03 May 2019 11:53 Antoniu Miclaus [Questions:] 08 Jan 2018 16:06 Doug Mercer add beta vs Vce plot08 Jan 2018 15:18 Doug Mercer [Questions:] 08 Jan 2018 15:11 Doug Mercer [NPN device Directions:] 08 Jan 2018 15:10 Doug Mercer [Background:] 13 Apr 2015 17:27 Doug Mercer created Next revision Both sides next revision Line 13: Line 13: =====Background:​===== =====Background:​===== - The variable analog outputs supplied by the ALM1000 hardware are voltages but can also measure current at same time. The BJT collector current, I<​sub>​C,​ is controlled by the very small base current, I<​sub>​B​. The generator output voltage must be converted into a suitable small current to drive the base terminal of the device under investigation. A simple high value resistor can be used to convert this voltage into a current, as shown in figure 1. However, only if the voltage across the resistor is known or controlled in some way. In this simple circuit, the base current I<​sub>​B​ = (CB-V - V<​sub>​BE​)/​10KΩ. We can set CB-V to known values but we don't know the exact value of V<​sub>​BE​. We can of course remove an estimate of the V<​sub>​BE​ mathematically. This is still only an estimate but close enough for our purposes here. + The variable analog outputs supplied by the ALM1000 hardware are voltages but can also measure current at same time. The Bipolar Junction Transistor can be modeled as a current controlled current source. The BJT collector current, I<​sub>​C,​ is controlled by the much smaller ​base current, I<​sub>​B​. The generator output voltage must be converted into a suitable small current to drive the base terminal of the device under investigation. A simple high value resistor can be used to convert this voltage into a current, as shown in figure 1. However, only if the voltage across the resistor is known or controlled in some way. In this simple circuit, the base current I<​sub>​B​ = (CB-V - V<​sub>​BE​)/​10KΩ. We can set CB-V to known values but we don't know the exact value of V<​sub>​BE​. We can of course remove an estimate of the V<​sub>​BE​ mathematically. This is still only an estimate but close enough for our purposes here. {{ :​university:​courses:​alm1k:​alm_lab4_f1.png?​600 |}} {{ :​university:​courses:​alm1k:​alm_lab4_f1.png?​600 |}} - ​Figure 1 NPN I<​sub>​C​ vs. V<​sub>​CE​ characteristic curve measurments​ + ​Figure 1 NPN I<​sub>​C​ vs. V<​sub>​CE​ characteristic curve measurements​ + + If we sweep the voltage on the collector, V<​sub>​CE,​ while changing the voltage on the resistor in a step wise fashion for each sweep cycle of the collector voltage, we can generate a set of characteristic curves of the collector current vs collector emitter voltage for a set of base currents. ​ ====Materials:​==== ====Materials:​==== Line 28: Line 30: ====NPN device Directions:​==== ====NPN device Directions:​==== - Build the simple characteristic curve measurement circuit shown in figure 1 on your solder-less breadboard. The green boxes indicate where to connect the M1000. + Build the simple characteristic curve measurement circuit shown in figure 1 on your solder-less breadboard. The green boxes indicate where to connect the ALM1000. ====Hardware Setup:==== ====Hardware Setup:==== Line 54: Line 56: ​Figure 2 PNP I<​sub>​C​ vs. V<​sub>​CE​ characteristic curve measurments​Figure 2 PNP I<​sub>​C​ vs. V<​sub>​CE​ characteristic curve measurments​ + + ====NPN Beta vs V<​sub>​CE​ Directions:​==== + + Beta (β) is defined as the ratio of the collector current, I<​sub>​C,​ to the base current, I<​sub>​B​. Beta is not constant and varies as the operating conditions of the transistor changes. In this experiment we will be plotting β vs V<​sub>​CE​. + + Change the 10 KΩ resistor in figure 1 to 1 KΩ. ====Questions:​==== ====Questions:​====

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