ExpEYES

The base current is set by the voltage from PV2, through a 100k resistor. The base voltage is measured to calculate the base current from Ib = (PV2-A2)/100K. The collector voltage is monitored by A1. The collector is connected to PV1, through a 1k resistor. For a selected base current, the voltage at PV1 is incremented in steps and at each step the collector voltage is measured. Corresponding collector current is calculated from i = (PV1-A1)/R. The transistor used is 2N2222, having a current gain of around 200. The schematic and photograph of the experimental setup and the results are shown below.

Python Program to generate the characteristics

Steps to perform this experiment manually are:

• Set the base current, by applying a volatge via the 100k resistor connected to the base.
• Set the voltage applied to the Collecter Vset, via the 1k resistor.
• Read the collector volatge Vc. Calculate Ic = (Vset-Vc)/R
• Increment Vset and repeat it until Vset is 5 volts (limit of our DC supply)
• Plot Vc against Ic
• Repeat the whole process for another base current.

The Python Program listed below implements the same steps.

import matplotlib.pyplot as plt

import eyes17.eyes
p = eyes17.eyes.open()

R = 1  # in kOhms, gives current in mA

for vb in [1,1.5,2]:
	p.set_pv2(vb)		# Set the base current
	x = []
	y = []
	v = 0.1
	while v < 5:
		p.set_pv1(v)
		vd = p.get_voltage('A1')
		i = (v-vd)/R
		x.append(vd)
		y.append(i)
		print (vd, i)
		v += 0.1
	plt.plot(x,y)

plt.show() 

Output of the program.

Program to plot Ib vs Ic Program to plot Ib vs Ic and find the gain by fitting the data