Datasheet

AD780
REV. B
–9–
NEGATIVE (–2.5 V OR –3.0 V) REFERENCE
The AD780 can produce a negative output voltage in shunt
mode, simply by connecting the input and output to ground
connecting the AD780’s GND pin to a negative supply via a
bias resistor as shown in Figure 18.
NC
TEMP
+V
IN
V
OUT
TRIM
GND
O/P SELECT
2.5V – NC
3.0V – GND
NC
1F
AD780
V–
–2.5 V
OUT
NOTE:
I
L
= LOAD CURRENT
I
S
MIN = MINIMUM SHUNT CURRENT
NC = NO CONNECT
V
OUT
– (V–)
I
L
+ I
S
MIN
R =
Figure 18. Negative (–2.5 V) Shunt Mode Reference
A precise –2.5 V (or –3.0 V) reference capable of supplying up
to 100 mA to a load can be implemented with the AD780 in se-
ries mode using the bootstrap circuit following.
AD780
2N3906
+5V
+5V
OP07
CONNECT IF
–3V OUTPUT
DESIRED
–5V
–2.5V (I
L
ⱕ 100mA)
–5V
OUT
1k
1000pF
V
IN
Figure 19. –2.5 V High Load Current Reference