SERIES-CONNECTED CURRENT SOURCES
CURRENT vs APPLIED VOLTAGE
+VS
101
High
100µA
100µA
100µA
100µA
Low
100µA/200µA
100
5
4
In
Out
Mirror
99
Com
3
0
10
20
30
40
50
60
70
80
Applied Voltage (V)
–VS
Compliance to –VS + 1.5V
Provides 2X Higher Compliance Voltage
FIGURE 6. Improved Low-Voltage Compliance.
FIGURE 7. 100µA Current Source—80V Compliance.
+VS
+VS
100µA
100µA
0.01µF
33kΩ
L
o
a
d
L
o
a
d
100µA
+VS
5.1V
100µA
1N4689
–VS
(b) Compliance to +VS – 5V.
–VS
(a) Compliance approximate
to Gnd. HV compliance
limited by FET breakdown.
L
o
a
d
1N4148
1N4148
27kΩ
High
–VS
(c)
40kΩ
40kΩ
100µA
100µA
0.01µF
0.01µF
±
±
0.01µF
0.01µF
100µA
100µA
40kΩ
40kΩ
Low
1N4148
1N4148
(d) Floating 200µA cascoded
current source.
(e) Bidirectional 200µA
cascoded current source.
NOTES: (1) FET cascoded current sources offer improved output impedance and high frequency operation. Circuit in (b)
also provides improved PSRR. (2) For current sinks (Circuits (a) and (b) only), invert circuits and use “N” channel JFETS.
FIGURE 8. FET Cascode Circuits.
®
7
REF200
BB [ BURR-BROWN CORPORATION ]
