TF EIMLab13 Writeup

DC Bipolar Transistor Curves

Data sheet for transistors.

Media:2N3904.pdfMedia:2N3906.pdf

Using 2N3904 is more straight forward in this lab.

Transistor circuit

Used to npn 2N3904 transister

1.) Identify the type (n-p-n or p-n-p) of transistor you are using and fill in the following specifications.

Value	Description
40 V	Collector-Base breakdown voltage
6 V	Emitter-Base Breakdown Voltage
40	Maximum Collector Voltage
200 mA	Maximum Collector Current
625 mW	Transistor Power rating([math]P_{Max}[/math])
30 - 300	DC current gain [math]h_{FE}( I_C, V_{CE})[/math]

2.) Construct the circuit below according to the type of transistor you have.

Let [math]R_E = 100 \Omega[/math].

[math]V_{CC} \lt 5 Volts[/math] variable power supply

[math]V_{BE}= 1V[/math].

I_B = 2[math] \mu[/math] A = 1V/500 k[math] \Omega[/math]

= 5[math] \mu[/math] A = 1V/200 k [math]\Omega[/math]

= 10 [math]\mu A[/math] = 1V/100 k [math]\Omega[/math]

3.) Measure the emitter current [math]I_E[/math] for several values of [math]V_{CE}[/math] by changing [math]V_{CC}[/math] such that the base current [math]I_B = 2 \mu[/math] A is constant. [math]I_B \approx \frac{V_{BB}-V_{b}}{R_B}[/math]

[math]R_{B} = 500 k \Omega[/math]

[math]R_{E} = 101 \Omega[/math]

[math]V_{BB} -V_B[/math]	[math]I_B[/math]	[math]V_{CC}[/math]	[math] V_ E[/math]	[math]I_E[/math]
V	[math]\mu[/math] A	V	mV	mA
1.007	2	0.0704	1.2
1.05	2	0.110	4.9
1.02	2	0.133	8.9
1.002	2	0.162	15.7
1.002	2	0.184	21.1
1.026	2	0.2287	32.3
1.012	2	0.3157	39.5
1.008	2	0.484	40.0
1.008	2	1.023	40.3
1.008	2	2.167	40.7
1.008	2	2.960	40.8
1.008	2	5.00	41.2

4.) Repeat the previous measurements for [math]I_B \approx 5 \mbox{ and } 10 \mu[/math] A. Remember to keep [math]I_CV_{CE} \lt P_{max}[/math] so the transistor doesn't burn out

[math]R_{B} = 201.8 k \Omega[/math]

[math]V_{BB} -V_B[/math]	[math]I_B[/math]	[math]V_{CC}[/math]	[math] V_ E[/math]	[math]I_E[/math]
V	[math]\mu[/math] A	V	mV	mA
1.044	5	0.094	7
1.053	5	0.134	19
1.026	5	0.167	32
1.003	5	0.200	47
1.003	5	0.234	62
1.02	5	0.269	77
1.0	5	0.289	83
1.07	5	0.442	101
1.02	5	0.721	99
1.02	5	1.04	100
1.02	5	1.94	100
1.02	5	2.96	101
1.02	5	3.72	102

[math]R_{B} = 100 k \Omega[/math]

[math]V_{BB} -V_B[/math]	[math]I_B[/math]	[math]V_{CC}[/math]	[math] V_ E[/math]	[math]I_E[/math]
V	[math]\mu[/math] A	V	mV	mA
0.942	10	0.227	78.1
1.005	10	0.245	94
0.995	10	0.267	108
1.068	10	0.31	138
1.005	10	0.355	160
0.996	10	1.032	197
1.002	10	0.688	197
0.996	10	2.175	199
0.994	10	3.283	200
0.992	10	4.66	202

5.) Graph [math]I_C[/math] -vs- [math]V_{CE}[/math] for each value of [math]I_B[/math] and [math]V_{CC}[/math] above. (40 pnts)

6.) Overlay points from the transistor's data sheet on the graph in part 5.).(10 pnts)

Questions

1.)Compare your measured value of [math]h_{FE}[/math] or [math]\beta[/math] for the transistor to the spec sheet? (10 pnts)

[math]\beta = \frac{I_C}{I_B} = \frac{0.5 mA}{0.002 mA} = 250[/math]

2.)What is [math]\alpha[/math] for the transistor?(10 pnts)

3.)The base must always be more _________(________) than the emitter for a npn (pnp)transistor to conduct I_C.(10 pnts)

4.)For a transistor to conduct I_C the base-emitter junction must be ____forward_______ biased.(10 pnts)

5.)For a transistor to conduct I_C the collector-base junction must be ______reverse_____ biased.(10 pnts)

Forest_Electronic_Instrumentation_and_Measurement