Agilent Technologies Option H48 Multiport Test Set Z5623A - Manual (Page 121)

Agilent Technologies Z5623A Option H48 7 -9
Advanced Topics
Using the Control Lines Connector
The DUT may require a control voltage that is different from any of the
existing power supply voltages. Rather than adding another power
supply, a circuit such as the one shown in
Figure 7-3 can be used to
derive the needed voltage from one of the existing power supply
outputs. The IC shown in the figure is a 3-Terminal Adjustable Voltage
Regulator (National Semiconductor Part No. LM317). It can supply a
maximum output current of 1.5 A provided that (V
IN
- V
OUT
)
≤ 15 V.
The equations governing the circuit shown in Figure 4-13 are
3 V ≤ (V
IN
- V
OUT
) ≤ 40 V
1.2 V
≤ V
OUT
V
C
= (1.25 V)(1 + R
2
/ R
1
) + I
ADJ
(R
2
)
I
ADJ
= 50 µA (typical)
The equations show that the circuit can be adjusted for any output
voltage (V
C
) from 1.2 V to 12.0 V provided that (a) a power supply
voltage of 15 V is used and (b) the values of R1 and R2 shown in Figure
7-3 are used.
Figure 7-3 Adjustable Voltage Regulator Circuit
In Out
Adjust
National Semiconductor
LM317
1 µF 1 µF
R
1
= 215 Ω
R
2
= 2 k
Ω
Power
Supply
V
C
+ +
V
C
can be adjusted from +1.2 to +12.0 V if Power Supply = +15 V