Lab 7 Characterization and DC Biasing of the BJT

ECEN 325 - 510

Lab 7: Characterization and DC Biasing of the BJT

Jonathan Yap

Objective:

The purpose of the lab is to investigate the behavior of the bipolar junction transistor. The characteristic NPN and PNP transistors will be designed along with four additional transistors using NPN and PNP junctions. Two of these specific circuits will include a single NPN or PNP junction and the other two circuits will include a cascaded NPN or PNP junction. The circuits should utilize a voltage source and resistors that fit the design parameters. Their behaviors will be compared with simulations, measurements, and calculations.

Calculations:

Schematics:

             NPN Characterization                                              PNP Characterization

             BJT DC Biasing NPN                                               BJT DC Biasing PNP

BJT Biasing NPN - Current Source                          BJT Biasing PNP - Current Source

Simulations:

Characteristic NPN I_C vs. V_BE Simulation     

Characteristic NPN I_C vs. V_CE Simulation     

Characteristic PNP I_C vs. V_BE Simulation      

Characteristic PNP I_C vs. V_CE Simulation      

          

BJT DC Biasing NPN I_CV_CV_REV₂ - Simulation        

BJT DC Biasing PNP I_CV_CV_REV₂ - Simulation        

BJT Biasing NPN: Current Source I_CV_CV_XV_YV₂ - Simulation              

BJT Biasing NPN: Current Source I_CV_CV_XV_YV₂ - Simulation        

Measurements:

Characteristic NPN I_C vs. V_BE Measurement      

Characteristic NPN I_C vs. V_CE Measurement      

Characteristic PNP I_C vs. V_BE Measurement       

Characteristic PNP I_C vs. V_CE Measurement      

BJT DC Biasing NPN I_C ( Calculated) V_C ( Channel 2) V_RE ( Channel 1) Measurement

BJT DC Biasing NPN V₂ ( Channel 2) V_RE ( Channel 1) Measurement

BJT DC Biasing PNP I_C ( Calculated) V_C ( Channel 2) V_RE ( Channel 1) Measurement

BJT DC Biasing PNP V₂ ( Channel 2) V_RE ( Channel 1) Measurement

BJT Current Bias NPN I_C (Calculated) V_C ( Channel 1) V₂ ( Channel 2) Measurement

BJT Current Bias NPN V_Y ( Channel 1) V_X ( Channel 2) Measurement

BJT Current Bias PNP I_C (Calculated) V_C ( Channel 1) V₂ ( Channel 2) Measurement

BJT Current Bias PNP V_X ( Channel 1) V_Y ( Channel 2) Measurement

Data Tables:

The characteristic NPN and PNP circuits will not have data tables due to excel plotting of their current and voltage functions. Comparisons will be drawn in the discussion section.

BJT DC Biasing NPN

Calculated	Simulated	Measured
V C (V)	1.5	1.51	1.53
V RE (V)	2	2.03	2.03
V 2 (V)	2.7	2.69	2.69
I C (mA)	1	1.01	1.01
RB1 (kΩ)	2.3	2.3	2.3
RB2 (kΩ)	2.7	2.7	2.7
RC (kΩ)	1.5	1.5	1.5
RE (kΩ)	2	2	2

BJT DC Biasing PNP

Calculated	Simulated	Measured
V C (V)	2	1.48	1.42
V RE (V)	2	1.99	1.90
V 2 (V)	2.7	2.69	2.52
I C (mA)	1	0.99	0.93
RB1 (kΩ)	2.3	2.3	2.3
RB2 (kΩ)	2.7	2.7	2.7
RC (kΩ)	1.5	1.5	1.5
RE (kΩ)	2	2	2

BJT Current Source Biasing NPN

Calculated	Simulated	Measured
V C (V)	1.5	1.49	1.35
V 2 (V)	2.7	2.69	2.50
V X (V)	2	2.01	1.71
V Y (V)	1.2	1.19	1.04
I C (mA)	2	1.99	1.94
RB1 (kΩ)	1.15	1.15	1.15
RB2 (kΩ)	1.35	1.35	1.35
RC (kΩ)	0.750	0.750	0.750
R3 (kΩ)	0.250	0.250	0.250
R2 (kΩ)	1.2	1.2	1.2
R1 (kΩ)	3.8	3.8	3.8

BJT Current Source Biasing PNP

Calculated	Simulated	Measured
V C (V)	1.5	1.39	1.18
V 2 (V)	2.7	2.69	2.07
V X (V)	2	1.97	1.75
V Y (V)	1.2	1.19	1.06
I C (mA)	2	1.85	1.57
RB1 (kΩ)	1.35	1.35	1.35
RB2 (kΩ)	1.15	1.15	1.15
RC (kΩ)	0.750	0.750	0.750
R3 (kΩ)	0.250	0.250	0.250
R2 (kΩ)	1.2	1.2	1.2
R1 (kΩ)	3.8	3.8	3.8

Discussion:

The calculations, simulations, and measured values for the characteristic PNP lined up very well. However, the characteristic NPN varied slightly. As seen in the I_C vs. V_CE graphs, the measured valued hit more of an asymptote at 1.2 Ma, whereas the simulated graph hit a maximum value at 1.4 mA. This could be due to a non-ideal PNP BJT which will be discussed further in other measurements. The calculated, simulated, and measured values for the DC sourced NPN BJT varied slightly and the measured values for the DC sourced PNP BJT varied more so. These variations were due to having non-ideal BJT’s and non-ideal resistors. Also, the current from the base was neglected in the calculations because the value was very small. This difference can be spotted greater in the current source BJT’s in the last part of the lab. The calculated, measured, and simulated values for the NPN and PNP current sourced BJT’s varied even more so that did in the DC sourced BJT’s. The BJT and the resistors with their large values and exact undetermined impedances affect the measured values as more are included in the circuit. This error can be minimized from 8%-15% usually to less than 1% with more ideal components and measurement tools.