Datasheet

REF03
Rev. G | Page 8 of 12
BOOST TRANSISTOR PROVIDES HIGH
OUTPUT CURRENT
When applications require more than 10 mA current delivery,
an external boost transistor may be added to the REF03 to pass
the required current without dissipating excessive power within
the IC. The maximum current output to the system is bounded
only by the capabilities of the boost transistor.
Figure 19 shows
this technique, with and without current limiting.
Current limiting may be used to prevent damage to the boost
transistor.
Figure 19A is an example of no current limit, while
Figure 19B shows the limit that occurs when the voltage dropped
across R2 exceeds one V
BE
(0.6 V). The current limit is sensitive
to the variations of the forward drop of the diodes and the
PNP’s V
BE
with temperature, and also decreases with increasing
temperature.
00372-019
REF03
V
IN
GND
2
4
6
V
OUT
65Ω
2N2905
–2.5V
V
+
2.49kΩ
2.49kΩ
A. NO CURRENT LIMIT B. CURRENT LIMITING
REF03
V
IN
GND
2
4
6
V
OUT
R2
10Ω
2N2905
R1
40Ω
–2.5V
0mA TO 100mA
V
–
1N4148
Figure 19. Output Current Boost
CMOS DAC REFERENCE
The REF03 makes an excellent reference for use with CMOS
and bipolar DACs.
Figure 20 shows the REF03 connected to
the
AD7393, a 12-bit CMOS DAC. An AD8603 with a common
mode input range that extends to its positive rail can be a good
combination with only 50 A of maximum current consumption.
REF03
V
IN
GND
2
4
6
V
OUT
AD7393
V
REF
GND
V
DD
+5
V
V
OUT
V
OUT
2.5V TO –2.5V
AD8603
–2.5V
470kΩ 470kΩ
00372-020
Figure 20. CMOS DAC Reference