NCP1200
Improving the Output Drive Capability
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2
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6
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The NCP1200 features an asymmetrical output stage used
to soften the EMI signature. Figure 22 depicts the way the
driver is internally made:
2N2222
2N2907
NCP1200
Rd
To Gate
V
CC
Q
2
7
40
Figure 23. Improving Both Turn–On and
Turn–Off Times
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5
1
2
3
4
8
7
6
5
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NCP1200
1N4148
Q\
3
To Gate
2N2907
Figure 22. The higher ON resistor slows down
the MOSFET while the lower OFF resistor
ensures fast turn–off.
In some cases, it is possible to expand the output drive
capability by adding either one or two bipolar transistors.
Figures 23, 24, and 25 give solutions whether you need to
improve the turn–on time only, the turn–off time or both. Rd
is there to damp any overshoot resulting from long copper
traces. It can be omitted with short connections. Results
showed a rise fall time improvement by 5X with standard
2N2222/2N2907:
Figure 24. Improving Turn–Off Time Only
1
2
3
4
8
7
NCP1200
2N2222
To Gate
6
5
1N4148
Figure 25. Improving Turn–On Time Only
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12
ETC [ ETC ]
