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MJL16218 Datasheet PDF : 8 Pages
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MJL16218
DYNAMIC DESATURATION
The SCANSWITCH series of bipolar power transistors are
specifically designed to meet the unique requirements of hor-
izontal deflection circuits in computer monitor applications.
Historically, deflection transistor design was focused on mini-
mizing collector current fall time. While fall time is a valid
figure of merit, a more important indicator of circuit perfor-
mance as scan rates are increased is a new characteristic,
“dynamic desaturation.” In order to assure a linear collector
current ramp, the output transistor must remain in hard satu-
ration during storage time and exhibit a rapid turn–off transi-
tion. A sluggish transition results in serious consequences.
As the saturation voltage of the output transistor increases,
the voltage across the yoke drops. Roll off in the collector
current ramp results in improper beam deflection and distor-
tion of the image at the right edge of the screen. Design
changes have been made in the structure of the SCAN-
SWITCH series of devices which minimize the dynamic
desaturation interval. Dynamic desaturation has been
defined in terms of the time required for the VCE to rise from
1.0 to 5.0 volts (Figures 9 and 10) and typical performance at
optimized drive conditions has been specified. Optimization
of device structure results in a linear collector current ramp,
excellent turn–off switching performance, and significantly
lower overall power dissipation.
+ 24 V
Table 2. High Resolution Deflection Application Simulator
C1 +
100 µF
U2
MC7812
VI
G
N
VO
D
+
C2
10 µF
Q2
MJ11016
(IB)
R1
1k
R5 (IC)
Q5
1k
MJ11016
R7
R8
R9
2.7 k
9.1 k
470
6.2 V
+ C3
R10
10 µF
47
C6 +
100 µF
LY
R2
R510
SYNC
R3
250
Q1
C4
C5
0.005
0.1 R11
76
470
(DC) OSC VCC
1W
8 % OUT 1
U1
R6
GND MC1391P
1k
2
BS170
T1: Ferroxcube Pot Core #1811 P3C8
Primary/Sec. Turns Ratio = 18:6
Gapped for LP = 30 µH
Q3
MJE
15031
100 V
T1
R12
470
1W
D1
MUR110
LB = 1.5 µH
CY = 0.01 µF
LY = 13 µH
5
D2
MUR460
LB
R4
22
CY
VCE
Q4
DUT
IB1 = 2.2 A
DYNAMIC DESATURATION TIME
4 IS MEASURED FROM VCE = 1 V
TO VCE = 5 V
3
IB2 = 4.5 A
2
TIME (2 µs/DIV)
Figure 11. Deflection Simulator Circuit Base
Drive Waveform
1
tds
0
0
2
4
6
8
10
TIME (ns)
Figure 12. Definition of Dynamic
Desaturation Measurement
6
Motorola Bipolar Power Transistor Device Data
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