Copyright
©
2005 LT. All rights reserved.
68
JFET SWITCH TEST
The JFET (Junction Field-Effect Transistor) is composed of input and output
circuits by using one of electrodes namely, Drain, Gate, or Source as the
common terminal. The JFET has different type for P or N channel switch. To
get the related data sheet from manufacturers will be highly recommended.
You can recognize the JFET by this meter. Following procedure may guide
you how to recognize JFET.
1. Set the rotary switch to "
Ω
" position.
2. Connect the red/ black test leads to "
Ω
" and "
" input terminals,
respectively. The “
Ω
” end of input provides positive test voltage.
3. Assume number 1, 2, and 3 for a TO-92 JFET as following Figure.
Figure- 52 TO-92 JFET
4.
Touch pin 1 and pin 2 by red and black probes, to get the value. Then
reverse the probes. If the two measuring value is < 1k
Ω
. You can assume
both pins would be Drain and Source poles. The residual pin 3 is Gate
pole. Always to find out which pin is Gate pole first. Refer to following
Table:
PIN
Probe Red/Black Probe Black/Red
Gate
1-2
<1k
Ω
<1k
Ω
3
1-3
<1k
Ω
<1k
Ω
2
2-3
<1k
Ω
<1k
Ω
1
5. To judge P-channel switch or N-channel, by constant voltage source and
verify the RDS (Drain-Source on Resistance). Normal, both channel types
will be switched when VGS) is equal to 0 V.
6. Connect the input probes to Drain and Source poles.
7. Then connect the red output alligator through a resistor of 100K
Ω
to Gate
pole, the black output alligator to black input probe.
8. If
the
R
DS
increased as the V (GS) is negative voltage, this JFET will be
N-channel. You can set DC power supply voltage output from
+00.000V
to
Most TO-92 JFET, the
pin 1 is always Drain.
Summary of Contents for MD-6520
Page 37: ...Copyright 2005 LT All rights reserved 33 Figure 25 Display of Dynamic Recording...
Page 44: ...Copyright 2005 LT All rights reserved 40 Figure 32 Peak Hold Display...
Page 48: ...Copyright 2005 LT All rights reserved 44 Figure 34 Selecting by Hz button...
Page 52: ...Copyright 2005 LT All rights reserved 48 Figure 37 Shift mA function by Blue button...
Page 54: ...Copyright 2005 LT All rights reserved 50 Figure 38 Line power Voltage measurement...
Page 62: ...Copyright 2005 LT All rights reserved 58 Figure 45 Resistance measurement...
Page 64: ...Copyright 2005 LT All rights reserved 60 Figure 46 Conductance measurement...
Page 66: ...Copyright 2005 LT All rights reserved 62 Figure 47 Forward Bias of Diode Measurement...
Page 67: ...Copyright 2005 LT All rights reserved 63 Figure 48 Reverse Bias of Diode Measurement...
Page 69: ...Copyright 2005 LT All rights reserved 65 Figure 49 Capacitance measurement...
Page 75: ...Copyright 2005 LT All rights reserved 71 Figure 55 Surface temperature measurement...
Page 93: ...Copyright 2005 LT All rights reserved 89 Figure 62 Battery charging procedures...