LAB 4: Diode and Transitor

We will determine the accuracy of the offset diode model and the load line to the actual experimental measurements for the diode, Zenor diode, and the BJT transitor. We will explain the i-v characteristics of the circuit and link them to the voltage across a resistor and the diode or transitor of test and its current.

wire

power supply (+6 and +20 scales needed)

1N4148 diode

Zenor diode

BJT transistor

two digital multimeters (DMM)

two alligator clips

protoboard

two banana jacks

- set up a circuit in series with 1 k ohm resistor and a 1N4148 diode

- calculate the Vr, Vd, and I by the offset diode model

- draw load line for Vr, Vd, and I to the diode’s I-V characteristics

- measure Vr, Vd, and I

1. Using the offset diode model:

I = 4.30 mA,

I = (Vs - 0.7 V)/ R = (5.00 V - 0.7 V) / (1 k ohm) = 4.30 mA

Vr = 4.30 V,

Vr = IR = Vs - 0.7 V = 4.30 V

Vd = 0.7 V,

Vd = Vs - Vr = 5.00 V - 4.30 V = 0.7 V

2.

table respect to diode current

table respect to diode voltage

Graph and load line : on the next page

3.

R1 = 986 ohms: range of resistor (5% tolerance): 950 to 1050 ohms

on +6 V power supply scale

Vs = 5.00 V

Vr = 4.34 V

Vd = 0.678 V

I = 4.38 V

3, 4) In this experiment, we see that the actual experiment measurement have higher values than does the load line and the offset diode model. This may be due to the 5% tolerance of the 1 k ohm resistor. However, the values are close pretty close to each other. If the resistor had a lower value, then the current flowing through the circuit would have a bigger value, by virtue of ohm’ law and that the load line on the graph would increase higher on the Id axis.

- set up a circuit in series with 1 k ohm resistor and a Zenor diode in forward-bias

- calculate the Vr, Vd, and I by the offset diode model

- draw load line for Vr, Vd, and I to the diode’s I-V characteristics

- measure Vr, Vd, and I

1. Using the offset diode model:

Zenor diode offset voltage in forward-bias: 0.8 V

I = 4.20 mA,

I = (Vs - 0.8 V)/ R = (5.00 V - 0.8 V) / (1 k ohm) = 4.20 mA

Vr = 4.20 V,

Vr = IR = Vs - 0.8 V = 4.20 V

Vd = 0.8 V,

Vd = Vs - Vr = 5.00 V - 4.20 V = 0.8 V

2.

table with respect to current of Zenor diode

table with respect to current of Zenor diode

table with respect to voltage of Zenor diode

graph and load line: on next page

3.

Vs = 5.00 V

Vr = 4.24 V

Vd = 0.778 V

I = 4.28 V

The measured values was predominantly close to the load line values for the voltage across the resistor and diode. The values between the measurement and offset diode model was not as close, but near the measured value. The currents between the offset diode model and the load line were lower than the measured valued. The reason of the differences is that the resistor has a 5% tolerance and that the offset diode model follows the ideal diode standard. The load line and actual measurement are not of ideal values, so have more accurate values to the diode’s behavior.

- set up a circuit in series with 1 k ohm resistor and a Zenor diode in reverse-bias

- calculate the Vr, Vd, and I by the offset diode model

- draw load line for Vr, Vd, and I to the diode’s I-V characteristics

- measure Vr, Vd, and I

1. Using the offset diode model:

Zenor diode offset voltage in reverse-bias: -5.40 V

- voltage from power supply is - 10.00 V

I = - 4.60 mA,

Is = (Vs - Vz) / Rs = ( -10 V - (-5.4 V))/ (1 k ohm) = - 4.60 V

Vr = - 4.60 V,

Vr = IR = Vs - (-5.4 V) = - 4.60 V

Vd = - 5.40 V,

Vd = Vs - Vr = - 10.00 V - ( - 4.60 V) = - 5.40 V

2. using load line

table with respect to current of Zenor diode

table with respect to current of Zenor diode

table with respect to voltage of Zenor diode

3.

Vs = - 10.00 V

Vr = - 4.67 V

Vd = - 5.37 V

I = - 4.72 V

The reverse-bias Zenor diode has a -5.40 offset voltage. All the comparing values had very close diode voltages of actuall -5.37 and ideal of -5.40. However, there was a larger error involving the voltage of the resistor. The tolerance of the resistor may have contributed to that difference. From the load line, we see if we increase the resistance. the voltage diode will have little change, but the current will decrease indefinitely.

- use +6 V and +20 power supply

- meause current of voltages in the transistor

R2 = 100.5 kohms

- To get mirco amps in the current readings, we use Ohm’s Law with the given values of Vce and the resistance of 100.5 k ohms.

Circuit Diagram

Comparisons

We see that the higher the base current, the higher the collector current. The collector current does not indeed increase at a rapid rate, in fact, it harly changes throughout the ce voltage.

In this lab, we learned how the offset diode model, the load line, and the actual measurement have so close values. We see that the offset diode model is of ideal values, and is not accurate to the actual behavior of the diode. We learned that the load line gives a very good approximation to the value of the actual measurement. We’ve learned that the transitor with a higher base current also has a higher collector current as well. We see that the load line is very important to the behavior of the diode and is used to predict the near values of the device.