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EE 3221 Lab #13

EE 3221 Lab #13 - 1 Connect the circuit in figure 1a Pick...

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1) Connect the circuit in figure 1a: Pick some value of Va and then change it so that Va-Vb changes by 1V. Readings: Va Vb Va-Vb ∆Vb rbe rbe=nVt/Ib 8.044V 0.6745V 7.369V -------- -------- 3.528k 7.040V 0.6713V 6.369V .0032V 3.2 kohms 4.082k rbe=∆Vb/1 micro amps=.0032/1 micro amps=3.2 kilo ohms Ib=(Va-Vb)/1Mohm=6.369/1Mohm=6.369 micro amps rbe=nVt/Ib=26mV/7.369 micro amps=3.528 kilo ohms rbe=nVt/Ib=26mV/6.369 micro amps=4.082 kilo ohms How much does Vb change? It changes .0032V. How does your measured value compare with the conventional formula? 3.2k compared to 4.082k. How does this compare to the diode resistance studied in experiment 3? For what theoretical value of Beta would 1 V be dissipated in the transistor? 2) Connect the circuit in figure 1b:

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Pick some value of Va and then change it so that Va-Vb changes by 1V. Readings: Va Vb Va-Vb ∆Vb rb rbe 8.015V 1.880V 6.134V -------- -------- 6.780V 1.645V 5.135V 0.235V 235 k rb=∆Vb/1 micro amps=.235/1 micro amps=235 kilo ohms What is the input resistance now? Rin=rb+BetaRe=235k+150(1k)=385k. How does it compare with the previous resistance? It is much higher.
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EE 3221 Lab #13 - 1 Connect the circuit in figure 1a Pick...

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