Measuring P-Channel MOSFET Characteristics

SYNC POWER CORP.
Technical Review of P-Channel
MOSFET Measurement
576 Curve Tracer
Testing Report
April 2005
Ver.1
MOSFET Products
AN001
1
Measuring P-Channel MOSFET Characteristics
Table of Contents
Page
1.
General Information................................................................................... 3
2.
Drain-Source Breakdown Voltage ( V(BR) , VDSS) ....................................... 5
3.
Zero Gate Voltage Drain Current Current ( IDSS )...................................... 9
4.
Gate Threshold Voltage ( VGS(th) ).............................................................. 11
5.
Gate Leakage Current ( IGSS ) .................................................................... 14
6.
Drain-Source On-Resistance RDS(ON) ........................................................... 17
7.
On-State Drain Current ID(ON) ................................................................... 21
8.
Diode Forward Voltage VSD ..................................................................... 25
This application note describes methods for measuring P-Channel MOSFET
Characteristics.
Prepared by :
Ian Lin
2
General Information
Type 576 Curve TRACER
VERTICAL
CURRENT/DVI
DISPLAY
OFFSET
MODE
POLARITY
HORIZONTAL
VOLTS/DIV
MAX
PEAK VOLTS
STEP
AMPLITUDE
SERIES
RESISTOR
VARIABLE
COLLECTOR
SUPPLY
CONNECTION
SELECTOR
LEFT/RIGHT
Figure 1.
The initial state of the curve tracer is assumed to be as follows:
• LEFT/ RIGHT switch in “off” position
• VARIABLE COLLECTOR SUPPLY at zero
• DISPLAY not inverted
• DISPLAY OFFSET set at zero
• STEP/OFFSET POLARITY button OUT (not inverted)
• VERT/HORIZ DISPLAY MAGNIFIER set at NORM (OFF)
• The REP button of the STEP FAMILY selector should be IN
• The AID button of the OFFSET selector should be IN
• The NORM button of the RATE SELECTOR should be IN
3
General Information
Figure 2.
z
BJT
MOSFET
Collector
Drain
Base
Gate
Emitter
Source
Figure 3.
Connect the device using the LEFT/RIGHT switch
Socket as follow
Figure 4.
Figure 5.
4
Drain-Source Breakdown Voltage
1.
Drain-Source Breakdown Voltage ( V(BR) , VDSS)
a.
b.
Set the MAX PEAK VOLTS to 75V.
Set the SERIES RESISTOR to limit the
avalanche current to a safe Value (i.e., tens
of milliamps). A suitable value in this case
would be 14k Ohms.
Figure 6.
c.
d.
Set the POLARITY switch to PNP.
The MODE control should be set to
NORM.
Figure 7.
e.
Set the DISPLAY to INVERT.
Figure 8.
5
Drain-Source Breakdown Voltage
f.
HORIZONTAL VOLTS/DIV should be set
at 5 V/div on the “collector” range.
Figure 9.
g.
VERTICAL CURRENT/DIV should be set
at 50 uA/div.
Figure 10.
h.
On the plug-in fixture, the CONNECTION
SELECTOR should be set to “SHORT” in
the “EMITTER GROUNDED” sector.This
action grounds the gate and disables the
step generator.
Figure 11.
6
Drain-Source Breakdown Voltage
i.
Connect the device using the LEFT/RIGHT
switch.
Figure 12.
j.
Increase the collector supply voltage using
the VARIABLECOLLECTOR SUPPLY
control until the current (as indicated by the
trace on the screen) reaches 250 uA. Read
VDSS from the screen.
Figure 13.
Figure 14.
7
Drain-Source Breakdown Voltage
Figure 15.
8
Zero Gate Voltage Drain Current Current ( IDSS )
2.
Zero Gate Voltage Drain Current Current ( IDSS )
a.
The MODE switch is set to“LEAKAGE”.
Figure 16.
b.
VERTICAL CURRENT/DIV should be set
at 1 nA/div.
Figure 17.
c.
Connect the device using the LEFT/RIGHT
switch and adjust the collector supply
voltage to the rated voltage of the Power .
Read the value of IDSS from the
display. The vertical sensitivity may need
altering to obtain an appropriately sized
display. Often IDSS will be in the nanoamp
range and the current observed will be
capacitor currents due to minute variations
in collector supply voltage
Figure 18.
9
Zero Gate Voltage Drain Current Current ( IDSS )
Figure 19.
Figure 20.
10
Gate Threshold Voltage ( VGS(th) )
3.
Gate Threshold Voltage ( VGS(th) )
a.
Connect the device as follows: source to “E”, gate to “B”, drain to “C”. This connection
arrangement may require the construction of a special test fixture. Bending of the device leads
can cause mechanical stress which results in the failure of the device.
Set the MAX PEAK VOLTS to 15V.
b. Set the SERIES RESISTOR to 30 ohms.
Figure 21.
c.
d.
e.
Set POLARITY to NPN.
Set the MODE CONTROL to NORM.
Not set the DISPLAY to INVERT.
Figure 22.
f.
Set the VERTICAL CURRENT/DIV to 50
uA/div.
Figure 23.
11
Gate Threshold Voltage ( VGS(th) )
g.
Set the HORIZONTAL VOLTS/DIV to
200mV/div.
Figure 24.
h.
i.
Set the CONNECTION SELECTOR to
“SHORT” in the “EMITTER
GROUNDED” sector.
Figure 25.
Connect the device using the LEFT/ RIGHT switch. Increase the VARIABLE COLLECTOR
VOLTAGE until the drain current reaches 250 uA as indicated by the trace on the screen. Read
the voltage on the horizontal center line (since this line corresponds to ID = 250 uA) .
Figure 26.
Figure 27.
12
Gate Threshold Voltage ( VGS(th) )
Figure 28.
Figure 29.
13
Gate Leakage Current ( IGSS )
4.
Gate Leakage Current ( IGSS )
a.
The device is connected as follows: gate to “C”, drain to “B”, source to “E”. This is not the
usual connection sequence, and a special test fixture will be required if bending of the leads is
to be avoided.
b.
c.
Set MAX PEAK VOLTS to 15V.
Set the SERIES RESISTOR to 30 ohms .
Figure 30.
d.
e.
f.
Set POLARITY to PNP.
Set the MODE switch to LEAKAGE.
Set the DISPLAY to INVERT.
Figure 31.
g.
Set the CONNECTION SELECTOR to the
“SHORT” position in the “EMITTER
GROUNDED” sector.
Figure 32.
14
Gate Leakage Current ( IGSS )
HORIZONTAL VOLTS/DIV should be set at 2V/div.
Figure 33.
h.
i.
VERTICAL CURRENT/DIV should be set to an appropriately low range.
Connect the device using the LEFT/RIGHT switch. Increase the collector supply voltage using
the VARIABLE COLLECTOR SUPPLY control, but do not exceed 20V, the maximum
allowable gate voltage. It may be necessary to adjust the vertical sensitivity. Read the leakage
current from the display . In many cases, the leakage current will be in the nanoamp range, in
which case the trace will be dominated by currents which flow through the device capacitance
as a result of minute fluctuations in the collector supply voltage.
j.
The above procedure is for determining gate leakage current with a positive gate voltage. To
make the same measurement using a negative voltage, reduce the VARIABLE COLLECTOR
SUPPLY voltage to zero, change the POLARITY switch to the PNP position, and reapply the
voltage. The trace will take time to settle because of the gate-source capacitance.
Figure 34.
Figure 35.
15
Gate Leakage Current ( IGSS )
Figure 36.
Figure 37.
16
Drain-Source On-Resistance RDS(ON)
5.
Drain-Source On-Resistance RDS(ON)
a.
b.
c.
Connect the device as follows: gate to “B”, drain to “C”, source to “E”.
Set the MAX PEAK VOLTS to 15 V.
Set the SERIES RESISTOR to 1.4 Ohms.
Figure 38.
d.
e.
The POLARITY switch should be set to
PNP.
The MODE switch should be set to
“NORM”
Figure 39.
f.
Set the DISPLAY to INVERT.
Figure 40.
17
Drain-Source On-Resistance RDS(ON)
Set the STEP AMPLITUDE to 0.5V.
g. Set NUMBER OF STEPS to 5.
h. Set OFFSET MULT to 0.
VGS= STEP AMPLITUDE x
( NUMBER OF STEPS + OFFSET
MULT)
= -0.5 x ( 5+0 )= -2.5V
if VGS= - 4.5V ,
Set NUMBER OF STEPS to 9.
Figure 41.
i.
j.
k.
l.
Set the HORIZONTAL VOLTS/DIV to
200mV/div.
The STEP MULTIPLIER button should be
OUT—that is, 0.1X not selected.
On the PULSED STEPS selector, the 80
microsec button should be IN (or the 300
microsec, if the 80 is not available).
On the RATE selector, the NORM button
should be IN.
Figure 42.
m. Set VERTICAL CURRENT/DIV at 500
mA/div . This scale should be chosen
according to the on-resistance of the device
being tested
Figure 43.
18
Drain-Source On-Resistance RDS(ON)
n.
HORIZONTAL VOLTS/DIV should be set
at 50mV/div
Figure 44.
o.
Set the CONNECTION SELECTOR to the
“STEP GEN” position in the “EMITTER
GROUNDED” sector.
p.
Figure 45.
Connect the device using the LEFT/RIGHT switch and raise the VARIABLE COLLECTOR
SUPPLY voltage until the desired value of drain current is obtained. RDS(on) is obtained from
the trace by reading the peak values of current and voltage.
Figure 46.
Figure 47.
19
Drain-Source On-Resistance RDS(ON)
q.
RDS(on) = VDS / ID
On the PULSED STEPS selector, the STEP
Figure 48.
On the PULSED STEPS selector, the 80uS
Figure 49.
Figure 50.
20
On-State Drain Current ID(ON)
6.
On-State Drain Current ID(ON)
a.
b.
c.
Connect the device as follows: gate to “B”, drain to “C”, source to “E”.
Set the MAX PEAK VOLTS to 15 V.
Set the SERIES RESISTOR to 1.4 Ohms.
Figure 51.
d.
e.
f.
The POLARITY switch should be set to
PNP.
The MODE switch should be set to
“NORM”.
Set the DISPLAY to INVERT.
Figure 52.
g.
h.
i.
Set the STEP AMPLITUDE to 0.5V.
Set NUMBER OF STEPS to 5.
Set OFFSET MULT to 0.
j.
VGS= STEP AMPLITUDE x ( NUMBER
OF STEPS + OFFSET MULT)
= -0.5 x ( 5+0 )= -2.5V
if VGS= - 4.5V
Set NUMBER OF STEPS to 9.
Figure 53.
21
On-State Drain Current ID(ON)
k.
Set VERTICAL CURRENT/DIV at 500
mA/div . This scale should be chosen
according to the on-resistance of the device
being tested.
Figure 54.
k.
HORIZONTAL VOLTS/DIV should be set
at 1V/div.
Figure 55.
l.
Set the CONNECTION SELECTOR to the
“STEP GEN” position in the “EMITTER
GROUNDED” sector.
Figure 56.
22
On-State Drain Current ID(ON)
m. Connect the device using the LEFT/RIGHT switch and raise the VARIABLE COLLECTOR
SUPPLY voltage until the desired value of drain current is obtained. RDS(on) is obtained from
the trace by reading the peak values of current and voltage.
Figure 57.
Figure 58.
Figure 59.
23
On-State Drain Current ID(ON)
Figure 60.
24
Diode Forward Voltage VSD
7.
Diode Forward Voltage VSD
a.
b.
c.
Connect the device as follows: gate to “B”, drain to “C”, source to “E”.
Set the MAX PEAK VOLTS to 15V.
Set the SERIES RESISTOR at 1.4 ohms or
a value sufficiently low that rated current
can be obtained.
Figure 61.
d.
e.
f.
Set POLARITY to NPN.
Set MODE to "NORM".
Not set the DISPLAY to INVERT.
Figure 62.
g.
The 80 microsec button of the PULSED
STEPS selector should be IN (or the 300
microsec, if the 80 is not available).
Figure 63.
25
Diode Forward Voltage VSD
h.
The CONNECTION SELECTOR should be
set to the "SHORT"position in the
“EMITTER GROUNDED” sector.
Figure 63.
i.
HORIZONTAL VOLTS/DIV should be on
100 mV/div.
Figure 64.
j.
VERTICAL CURRENT DIV should be on
200 mA/div.
Figure 65.
26
Diode Forward Voltage VSD
k.
The device is connected using the LEFT/RIGHT switch. Increase the VARIABLE
COLLECTOR SUPPLY voltage until rated current is reached . Read VSD from the trace .
Figure 66.
Figure 67.
Figure 68.
Figure 69.
27
Measuring P-Channel MOSFET Characteristics
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