I-V Curve: Transistor A transistor is a semiconductor device used to amplify or switch electronic signals and power. It is composed of a semiconductor material, usually with at least three terminals to connect to the external circuit [wikipedia]. The simple I-V tracer built for the Ohm's law experiments [link] was tested for its ability to plot BC337 transistor's I-V characteristic (Python code and graph below).

#Example Python code to demostrate ohm low. 

from I2Brick import *
import matplotlib.pyplot as plt
%matplotlib inline

port = I2Brick('COM4')             #Windows: Initialize serial communication with I2Bricks
#port = I2Brick('/dev/ttyUSB0')    #Linux: Initialize serial communication with I2Bricks

print(ard(port))                   #test communication between ARD and PC

R_sense=100
voltage5=[]
voltage10=[]
voltage15=[]
voltage20=[]
voltage25=[]
current5=[]
current10=[]
current15=[]
current20=[]
current25=[]

# I-V Curve for 5 microAmper
dac(port,1, 1320)              #set dac voltage (for base current=5 microAmper)
for v in range (0, 4000,25):
    dac(port,0, v)               #set dac voltage
    ADC0 = adc(port,0)              #read adc0 voltage
    ADC1 = adc(port,1)
    if (ADC0<0 or ADC0>4096): ADC0 = 0
    if (ADC1<0 or ADC1>4096): ADC1 = 0
    voltage5.append((ADC0 - ADC1)/1000)   #calculate voltage
    current5.append(ADC1/R_sense)        #calculate current

# I-V Curve for 10 microAmper
dac(port,1, 2015)               #set dac voltage (for base current=10 microAmper)
for v in range (0, 4000,25):
    dac(port,0, v)               #set dac voltage
    ADC0 = adc(port,0)              #read adc0 voltage
    ADC1 = adc(port,1)
    if (ADC0<0 or ADC0>4096): ADC0 = 0
    if (ADC1<0 or ADC1>4096): ADC1 = 0
    voltage10.append((ADC0 - ADC1)/1000)   #calculate voltage
    current10.append(ADC1/R_sense)        #calculate current

# I-V Curve for 15 microAmper
dac(port,1, 2715)               #set dac voltage (for base current=15 microAmper)
for v in range (0, 4000,25):
    dac(port,0, v)               #set dac voltage
    ADC0 = adc(port,0)              #read adc0 voltage
    ADC1 = adc(port,1)
    if (ADC0<0 or ADC0>4096): ADC0 = 0
    if (ADC1<0 or ADC1>4096): ADC1 = 0
    voltage15.append((ADC0 - ADC1)/1000)   #calculate voltage
    current15.append(ADC1/R_sense)        #calculate current

# I-V Curve for 20 microAmper
dac(port,1, 3415)               #set dac voltage (for base current=20 microAmper)
for v in range (0, 4000,25):
    dac(port,0, v)               #set dac voltage
    ADC0 = adc(port,0)              #read adc0 voltage
    ADC1 = adc(port,1)
    if (ADC0<0 or ADC0>4096): ADC0 = 0
    if (ADC1<0 or ADC1>4096): ADC1 = 0
    voltage20.append((ADC0 - ADC1)/1000)   #calculate voltage
    current20.append(ADC1/R_sense)        #calculate current
    
# I-V Curve for 25 microAmper
dac(port,1, 4095)              #set dac voltage (for base current=25 microAmper)
for v in range (0, 4000,25):
    dac(port,0, v)               #set dac voltage
    ADC0 = adc(port,0)              #read adc0 voltage
    ADC1 = adc(port,1)
    if (ADC0<0 or ADC0>4096): ADC0 = 0
    if (ADC1<0 or ADC1>4096): ADC1 = 0
    voltage25.append((ADC0 - ADC1)/1000)   #calculate voltage
    current25.append(ADC1/R_sense)        #calculate current

    
dac(port,0, 0)               
dac(port,1, 0)               
port.close()

plt.plot(voltage25, current25,label='25 microamper')
plt.plot(voltage20, current20,label='20 microamper')
plt.plot(voltage15, current15,label='15 microamper')
plt.plot(voltage10, current10,label='10 microamper')
plt.plot(voltage5, current5,label='5 microamper')

plt.axis([0,5,0,10])
plt.title('i-v curve for BC337')
plt.legend()
plt.xlabel('Voltage [V]')
plt.ylabel('Current [mA]')
plt.show()

I2Brick Firmware 3.0. Supported brick: ARD, OLD, DAC, ADC

DCA75 Pro Advanced Semiconductor Analyser For comparison, the BC337 transistor was also tested with a Peak Electronics Atlas DCA75 Pro Advanced Semiconductor Analyser (right).

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