experiment 9: bipolar and field effect … · transistors, and will learn to use the transistor...

BIPOLAR AND FET TRANSISTORS 11/3/10

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EXPERIMENT 9: BIPOLAR AND FIELD EFFECT TRANSISTOR CHARACTERISTICS In this experiment we will study the characteristics of bipolar and junction field-effect (JFET) transistors, and will learn to use the transistor curve tracer.

Be sure to observe the proper orientation of leads when you install the transistors in the test setup and the curve tracer.

PNP BIPOLAR N-CHANNEL FET view from below view from below

(leads point toward you!) (leads point toward you!) Note that if you hold it so it looks like a “D”, FET lead arrangement is less the leads are the same position as in schematic. standard -- need to check data sheet! I. THE BIPOLAR TRANSISTOR The circuit we will use to measure the properties of a silicon PNP transistor (model 2N3906) is shown below. Use a DC power supply for V0. For ammeter IB use a VOM on the 0-50 µA scale; for IE use a second VOM with the scale set to 1, 10, or 100 mA as needed. Use digital meters to measure the voltages VBE and VCE.

g s

d


2

1. The first step is to measure IE and VBE as a function of the base current for a fixed value of VCE.

Turn the 10 kΩ pot all the way down (i.e., full counter-clockwise). Next, connect the ammeters being careful to observe the proper polarity and then connect up the power supply, again being careful to observe the polarity. Make the remaining connections, and then turn on the power supply and adjust V0 so that VCE = −12 V. By adjusting the pot you can change the base-to-emitter voltage, VBE, and hence the base current IB.

Measure and tabulate IE and VBE as a function of IB taking 2 µA steps for 0 ! IB ! 10 µA and 5 µA steps for 10 µA ! IB ! 50 µA. You will notice that VBE drifts slowly for some time after IB is increased or decreased. This drift is due to the temperature change caused by the power dissipation in the transistor. After each change in IB you should pause briefly to allow the temperature to stabilize before taking the readings.

You will also notice that VCE changes some (particularly when you change scales on the ammeter IE). You may reset VCE to −12 V at each step if you want, but it is also all right to just ignore the changes, since IE and VBE are nearly independent of VCE.

Calculate hFE (or β) at each point from the formula β = IE/IB and make a graph of β as a function of IE.

2. Optional: (This is a long lab. Come back to this if you have time at the end.) For signal

transistors such as the one we use in this experiment, the relationship between VBE and IE (or IC) is given approximately by:

( )BE kTV /V

E 0I I e 1= !

provided that T is constant (I0 and VkT both depend on temperature). Make a graph of IE vs VBE on semilog paper, and verify that the low-current (i.e. constant temperature) portion of the graph is linear. Determine the quantity VkT from the slope of the linear part of the graph, assuming that VBE/VkT 1. How does your result compare with the expected value, VkT = kT/e = 26 mV?

3. The quantities IE and VBE are approximately independent of VCE. In this step we will measure

two parameters, the output admittance (hoe) and the reverse voltage ratio (hre) that give the sensitivity of IE and VBE to changes in VCE.

Adjust the power supply voltage V0 to obtain VCE = −8 V, and then adjust the 10 kΩ pot to get IB 15 µA. Record the values of IE, IB, VBE and VCE. Then adjust the power supply and the pot to get VCE = −16 V and the same value of IB that you had for the first measurement, and record the parameters again.


3

Calculate the output admittance,

[ ]oe E CE Bh I / V constant I= ! ! ,

and the reverse voltage ratio,

[ ]re BE CE Bh V / V constant I= ! ! .

Typical values for these parameters are hoe ~ 10-4 S and hre ~ 5-10 x 10−4.

4. The input impedance of the transistor (hie or rin) can be measured as follows. Keeping VCE

constant (at −8 V for example) set IB to 6 µA and then l0 µA, and record the values of IE and VBE at each point. Calculate hie for your transistor from:

[ ]ie BE B CE

h V / I constant V= ! !

A typical value for this parameter is 3.5 kΩ.

5. As discussed in class, the input impedance is related to hfe (or β) and a quantity called the

transresistance according to rin = hfe rtr. Calculate hfe = ΔIE/ΔIB from the measurements taken in step 4 and determine the transresistance. Compare your result with the calculated transresistance, rtr = 26 mV/IE where IE is the average of the two values from step 4.

6. Using the transistor curve tracer, measure the collector characteristics of your transistor. The

curve tracer generates a plot of IC vs VCE for several values of IB. The Appendix to this experiment describes how to set up the curve tracer for bipolar transistors and FET’s. Make a copy of the curve tracer output and tape the picture in your notebook. Label the axes with the name of the quantity plotted and also indicate the scale. Label each curve with the appropriate value of IB.

From the curve tracer plot determine the value of β for IB = 20 µA and VCE = −12 V. Compare the result with the value you got in step 1.


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II. THE FIELD EFFECT TRANSISTOR In this section we will measure some of the properties of an n-channel junction field-effect transistor (model J309). 1. Use the transistor curve tracer to obtain a plot of the drain characteristics for the FET. The curve

tracer plots ID vs VDS for several values of VGS. Make a copy of the curve tracer output, tape it in your notebook, label the scales, and indicate the appropriate value of VGS for each curve. The characteristics of a given FET can vary widely from the “typical” values given in the Appendix to this experiment.

Note: the rest of step 1 and steps 2,3,4 are optional. Do them if you have time after completing step 2 of the bipolar transistor part.

Before going on to step 2, consult with your instructor to see if the procedure given below needs to be modified for the particular FET you are using.

Set the circuit board as shown in the diagram above. For an FET the gate and drain voltages must have opposite signs, and therefore we need to use two power supplies.

Start by turning the 10 kΩ pot fully CCW. Ground the negative terminal of the V1 supply and the positive terminal of the V2 supply. As in section I, we will use VOM’s to measure the current, and digital meters to measure the voltages. After making all the connections, turn on the power supply and set V2 to about −8 volts.

2. An FET can be used as a “variable resistor”, in which the resistance of the drain-source channel is adjusted by varying the gate voltage, VGS. In this step we will measure the resistance of the channel for VGS = 0.


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With the pot fully CCW you should get VGS = 0. Vary VDS (by adjusting V1) from 0 to +2.0 V in 0.2 V steps, and make a plot of ID vs VDS. Determinethe drain-source resistance, RDS, from the ohmic (linear) region of the plot.

From the curve tracer plot generated in step 1, determine whether RDS increases or decreases when the gate voltage is decreased.

3. Next we will measure some of the characteristics of the FET in the “pinch-off” region. In this

region ID is essentially independent of VDS (i.e. the transistor acts like a constant current source). This is the region where an FET can be used as an amplifier.

Set VGS to −1.5 V by adjusting the 10 kΩ pot, and then vary VDS from +2 V to +20 V in 2 V steps. As you make the measurements notice that (as expected) the gate current is essentially zero. Make a plot of ID vs VDS.

For a constant current source, the output impedance should be large. Determine the output impedance of the FET in the pinch-off region,

r0S = ΔVDS/ΔID ,

by using your measurements at VDS = +10 V and +20 V. 4. FET’s are sometimes used as switches or gates. The switch is closed when VGS = 0 and open

when VGS exceeds some cutoff value VGS(off) . With VDS = +12 V, vary the pot to change the gate-source voltage, VGS. Measure and tabulate ID as a function of VGS for VGS = 0 V to the cutoff voltage using 0.5 V steps for VGS (you may want to adjust V1 at each step to maintain VDS = +12 V). Plot ID vs VGS (the graph should be approximately parabolic) and determine the cutoff voltage.

CURVE TRACER APPENDIX The table below indicates the appropriate Curve Tracer settings. 2N3904 2N3906 J309

Collector Sweep or Drain Sweep (FET)

20 V 20 V 20 V

Current Sensitivity (Signal)

10 mA/V 10 mA/V 10 mA/V

Selector

Transistor Transistor FET

Polarity

NPN PNP N Channel

Base Current or Gate Voltage

10 µA/step

10 µA/step

0.5 V/step

CB E

TO-92

C

B

E

BC

C

SOT-223

E

PNP General Purpose AmplifierThis device is designed for general purpose amplifier and switchingapplications at collector currents of 10 µA to 100 mA.

Absolute Maximum Ratings* TA = 25°C unless otherwise noted

*These ratings are limiting values above which the serviceability of any semiconductor device may be impaired.

Symbol Parameter Value UnitsVCEO Collector-Emitter Voltage -40 VVCBO Collector-Base Voltage -40 VVEBO Emitter-Base Voltage -5.0 VIC Collector Current - Continuous -200 mATJ, Tstg Operating and Storage Junction Temperature Range -55 to +150 °C

2010 Fairchild Semiconductor Corporation

Thermal Characteristics TA = 25°C unless otherwise noted

Symbol Characteristic Max Units2N3906 *MMBT3906 **PZT3906

PD Total Device DissipationDerate above 25°C

6255.0

3502.8

1,0008.0

mWmW/°C

RθJC Thermal Resistance, Junction to Case 83.3 °C/WRθJA Thermal Resistance, Junction to Ambient 200 357 125 °C/W

*Device mounted on FR-4 PCB 1.6" X 1.6" X 0.06."

**Device mounted on FR-4 PCB 36 mm X 18 mm X 1.5 mm; mounting pad for the collector lead min. 6 cm2.

2N3906 MMBT3906

SOT-23Mark: 2A

PZT3906

2N3906 / M

MB

T3906 / PZT3906

NOTES:1) These ratings are based on a maximum junction temperature of 150 degrees C.2) These are steady state limits. The factory should be consulted on applications involving pulsed or low duty cycle operations.

2N3906/MMBT3906/PZT3906, Rev A1

Electrical Characteristics TA = 25°C unless otherwise noted

Symbol Parameter Test Conditions Min Max Units

OFF CHARACTERISTICS

ON CHARACTERISTICS

SMALL SIGNAL CHARACTERISTICS

SWITCHING CHARACTERISTICS

V(BR)CEO Collector-Emitter Breakdown Voltage* IC = -1.0 mA, IB = 0 -40 VV(BR)CBO Collector-Base Breakdown Voltage IC = -10 µ A, IE = 0 -40 VV(BR)EBO Emitter-Base Breakdown Voltage IE = -10 µ A, IC = 0 -5.0 VIBL Base Cutoff Current VCE = -30 V, V BE = -3.0 V -50 nAICEX Collector Cutoff Current VCE = -30 V, V BE = -3.0 V -50 nA

hFE DC Current Gain * IC = -0.1 mA, VCE = -1.0 VIC = -1.0 mA, V CE = -1.0 VIC = -10 mA, V CE = -1.0 VIC = -50 mA, V CE = -1.0 VIC = -100 mA, V CE = -1.0 V

60801006030

300

VCE(sat) Collector-Emitter Saturation Voltage IC = -10 mA, IB = -1.0 mAIC = -50 mA, IB = -5.0 mA

-0.25-0.4

VV

VBE(sat) Base-Emitter Saturation Voltage IC = -10 mA, IB = -1.0 mAIC = -50 mA, IB = -5.0 mA

-0.65 -0.85-0.95

VV

fT Current Gain - Bandwidth Product IC = -10 mA, V CE = -20 V,f = 100 MHz

250 MHz

Cobo Output Capacitance VCB = -5.0 V, IE = 0,f = 100 kHz

4.5 pF

Cibo Input Capacitance VEB = -0.5 V, IC = 0,f = 100 kHz

10.0 pF

NF Noise Figure IC = -100 µ A, VCE = -5.0 V,RS =1.0 k Ω, f=10 Hz to 15.7 kHz

4.0 dB

td Delay Time VCC = -3.0 V, V BE = -0.5 V, 35 nstr Rise Time IC = -10 mA, IB1 = -1.0 mA 35 nsts Storage Time VCC = -3.0 V, IC = -10 mA 225 ns

tf Fall Time IB1 = IB2 = -1.0 mA 75 ns

Spice ModelPNP (Is=1.41f Xti=3 Eg=1.11 Vaf=18.7 Bf=180.7 Ne=1.5 Ise=0 Ikf=80m Xtb=1.5 Br=4.977 Nc=2 Isc=0 Ikr=0Rc=2.5 Cjc=9.728p Mjc=.5776 Vjc=.75 Fc=.5 Cje=8.063p Mje=.3677 Vje=.75 Tr=33.42n Tf=179.3p Itf=.4 Vtf=4Xtf=6 Rb=10)

*Pulse Test: Pulse Width ≤ 300 µs, Duty Cycle ≤ 2.0%

2N3906 / M

MB

T3906 / PZT3906PNP General Purpose Amplifier

(continued)

2N3906 / M

MB

T3906 / P

ZT

3906

Typical Characteristics

Common-Base Open Circuit Input and Output Capacitance

vs Reverse Bias Voltage

0.1 1 100

2

4

6

8

10

REVERSE BIAS VOLTAGE (V)

CA

PA

CIT

AN

CE

(p

F)

C obo

C ibo

PNP General Purpose Amplifier(continued)

Typical Pulsed Current Gainvs Collector Current

0.1 0.2 0.5 1 2 5 10 20 50 10050

100

150

200

250

I - COLLECTOR CURRENT (mA)

h

- T

YP

ICA

L P

UL

SE

D C

UR

RE

NT

GA

IN

C

FE

125 °C

25 °C

- 40 °C

V = 1.0VCE

Collector-Emitter SaturationVoltage vs Collector Current

1 10 100 2000

0.05

0.1

0.15

0.2

0.25

0.3

I - COLLECTOR CURRENT (mA)V

-

CO

LL

EC

TO

R E

MIT

TE

R V

OL

TAG

E (

V)

C

CES

AT

25 °C

- 40 °C

125°C

β = 10

Base-Emitter SaturationVoltage vs Collector Current

1 10 100 2000

0.2

0.4

0.6

0.8

1


V

-

BA

SE

EM

ITT

ER

VO

LTA

GE

(V

)

C

BES

AT

β = 10

25 °C

- 40 °C

125 °C

Base Emitter ON Voltage vsCollector Current

0.1 1 10 250

0.2

0.4

0.6

0.8

1

I - COLLECTOR CURRENT (mA)V

- B

AS

E E

MIT

TE

R O

N V

OL

TAG

E (

V)

C

BE

(ON

)

V = 1VCE

25 °C

- 40 °C

125 °C

Collector-Cutoff Currentvs Ambient Temperature

25 50 75 100 1250.01

0.1

1

10

100

T - AMBIENT TEMPERATURE ( C)

I

-

CO

LLE

CT

OR

CU

RR

EN

T (

nA

)

A

CB

O

°

V = 25VCB

Power Dissipation vsAmbient Temperature

0 25 50 75 100 125 1500

0.25

0.5

0.75

1

TEMPERATURE ( C)

P

- PO

WE

R D

ISS

IPA

TIO

N (

W)

D

o

SOT-223

SOT-23

TO-92

Typical Characteristics (continued)

Noise Figure vs Frequency

0.1 1 10 1000

1

2

3

4

5

6

f - FREQUENCY (kHz)

NF

- N

OIS

E F

IGU

RE

(d

B)

I = 100 µA, R = 200ΩC

V = 5.0VCE

S

I = 100 µA, R = 2.0 kΩC S

I = 1.0 mA, R = 200ΩC S

Noise Figure vs Source Resistance

0.1 1 10 1000

2

4

6

8

10

12

R - SOURCE RESISTANCE ( )

NF

- N

OIS

E F

IGU

RE

(d

B)

kΩ

I = 100 µAC

V = 5.0Vf = 1.0 kHz

CE

I = 1.0 mAC

S

Switching Timesvs Collector Current

1 10 1001

10

100

500


TIM

E (

nS

)

I = I = t r

t s

B1

C

B2I c

10

t f

t d

Turn On and Turn Off Timesvs Collector Current

1 10 1001

10

100

500


TIM

E (

nS

)

I = I =

t off

B1 B2I c

10

t on

V = 0.5VBE(OFF)

t I = on

t off

B1I c

10

2N3906 / M

MB

T3906 / P

ZT

3906PNP General Purpose Amplifier

(continued)

2N3906 / M

MB

T3906 / P

ZT

3906

Typical Characteristics (continued)

PNP General Purpose Amplifier(continued)

Input Impedance

0.1 1 100.1

1

10


h

- IN

PU

T IM

PE

DA

NC

E (

k )

V = 10 VCE

C

ie

f = 1.0 kHzΩ

Output Admittance

0.1 1 1010

100

1000


h

- O

UT

PU

T A

DM

ITTA

NC

E (

mho

s) V = 10 VCE

C

oe

f = 1.0 kHz

µ

Current Gain

0.1 1 1010

20

50

100

200

500

1000


h

- C

UR

RE

NT

GA

IN

V = 10 VCE

C

fe

f = 1.0 kHz

Voltage Feedback Ratio

0.1 1 101

10

100


h

- V

OLT

AG

E F

EE

DB

AC

K R

AT

IO (

x10

)

C

re_

4

G

D

S

J309J310

N-Channel RF AmplifierThis device is designed for VHF/UHF amplifier, oscillator and mixerapplications. As a common gate amplifier, 16 dB at 100 MHz and12 dB at 450 MHz can be realized. Sourced from Process 92.

Absolute Maximum Ratings* TA = 25°C unless otherwise noted

*These ratings are limiting values above which the serviceability of any semiconductor device may be impaired.

NOTES:1) These ratings are based on a maximum junction temperature of 150 degrees C.2) These are steady state limits. The factory should be consulted on applications involving pulsed or low duty cycle operations.

Thermal Characteristics TA = 25°C unless otherwise noted

MMBFJ309MMBFJ310

Symbol Parameter Value UnitsVDS Drain-Source Voltage 25 V

VGS Gate-Source Voltage - 25 V

IGF Forward Gate Current 10 mA

TJ ,Tstg Operating and Storage Junction Temperature Range -55 to +150 °C

SOT-23Mark: 6U / 6T

GS D

TO-92

*Device mounted on FR-4 PCB 1.6" X 1.6" X 0.06."

1997 Fairchild Semiconductor Corporation

NOTE: Source & Drain are interchangeable

J309 / J310 / MM

BF

J309 / MM

BF

J310

Symbol Characteristic Max UnitsJ309-J310 *MMBFJ309-310

PD Total Device DissipationDerate above 25°C

6255.0

3502.8

mWmW/°C

RθJC Thermal Resistance, Junction to Case 125 °C/W

RθJA Thermal Resistance, Junction to Ambient 357 556 °C/W

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Electrical Characteristics TA = 25°C unless otherwise noted

OFF CHARACTERISTICS

Symbol Parameter Test Conditions Min Typ Max Units

V(BR)GSS Gate-Source Breakdown Voltage IG = - 1.0 µA, VDS = 0 - 25 V

IGSS Gate Reverse Current VGS = - 15 V, VDS = 0VGS = - 15 V, VDS = 0, TA =125°C

- 1.0- 1.0

nAµA

VGS(off) Gate-Source Cutoff Voltage VDS = 10 V, ID = 1.0 nA 309310

- 1.0- 2.0

- 4.0- 6.5

VV

ON CHARACTERISTICSIDSS Zero-Gate Voltage Drain

Current*VDS = 10 V, VGS = 0 309

3101224

3060

mAmA

VGS(f) Gate-Source Forward Voltage VDS = 0, IG = 1.0 mA 1.0 V

SMALL SIGNAL CHARACTERISTICS

*Pulse Test: Pulse Width ≤ 300 µs, Duty Cycle ≤ 2.0%

Re(yis) Common-Source InputConductance

VDS = 10, ID = 10 mA, f = 100 MHz309310

0.70.5

mmhosmmhos

Re(yos) Common-Source OutputConductance

VDS = 10, ID = 10 mA, f = 100 MHz 0.25 mmhos

Gpg Common-Gate Power Gain VDS = 10, ID = 10 mA, f = 100 MHz 16 dB

Re(yfs) Common-Source ForwardTransconductance

VDS = 10, ID = 10 mA, f = 100 MHz 12 mmhos

Re(yig) Common-Gate Input Conductance VDS = 10, ID = 10 mA, f = 100 MHz 12 mmhos

gfs Common-Source ForwardTransconductance

VDS = 10, ID = 10 mA, f = 1.0 kHz309310

10,0008000

20,00018,000

µmhosµmhos

goss Common-Source OutputConductance

VDS = 10, ID = 10 mA, f = 1.0 kHz 150 µmhos

gfg Common-Gate ForwardConductance

VDS = 10, ID = 10 mA, f = 1.0 kHz309310

13,00012,000

µmhosµmhos

gog Common-Gate OutputConductance

VDS = 10, ID = 10 mA, f = 1.0 kHz309310

100150

µmhosµmhos

Cdg Drain-Gate Capacitance VDS = 0, VGS = - 10 V, f = 1.0 MHz 2.0 2.5 pF

Csg Source-Gate Capacitance VDS = 0, VGS = - 10 V, f = 1.0 MHz 4.1 5.0 pF

NF Noise Figure VDS = 10 V, ID = 10 mA,f = 450 MHz

3.0 dB

en Equivalent Short-Circuit InputNoise Voltage

VDS = 10 V, ID = 10 mA,f = 100 Hz

6.0

N-Channel RF Amplifier(continued)

nV/√Hz

J309 / J310 / MM

BF

J309 / MM

BF

J310

Typical Characteristics

Transfer Characteristics Transfer Characteristics

Transfer Characteristics

Forward Transadmittance

Transfer Characteristics

Input Admittance

J309 / J310 / MM

BF

J309 / MM

BF

J310N-Channel RF Amplifier

(continued)


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experiment 9: bipolar and field effect … · transistors, and will learn to use the transistor...

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