03 | Keysight | Low Current Semiconductor Measurements
Using the B2980A Series Ammeter - Technical Overview
Measurement Basics and the B2980A Series Performance
1. Low noise, low impedance and low current ammeter provides stable
measurement data
The B2980A Series ammeter has the following features:
–
The B2980A’s low noise design achieves better than 100 aA current measurement (with 10 aA minimum
resolution).
–
The low input resistance and low offset voltage allow a faster measurement response and more accurate
measurement results.
These features provide the B2980A Series ammeter with the ability to perform stable measurements
across a wide range of applications (especially very low current measurements).
2. Floating ammeter design provides stable measurements for both loating
and grounded DUTs
The B2980A Series ammeter employs a loating design to provide stable measurements and a
lexible coniguration for low current measurement applications.
Floating DUT coniguration
Figure 1 shows a circuit block diagram using the loating ammeter with a DC voltage source supply
-
ing current to the device under test (DUT). The ammeter common is connected to the inner shield of
the ammeter’s triaxial input, while the outer shield/conductor is connected to the instrument chassis.
The chassis is connected to earth ground through the power cable ground connection.
In the Figure 1 example the DUT is loating, with the DC source connected at one end and the
ammeter connected at the other end. Since the ammeter is not connected to earth ground, any com-
mon noise generated in the DC source ground loop does not low into the ammeter. Therefore, the
ammeter’s loating design minimizes the impact of ground noise interference on the measurements.
A
A
-
+
DUT
Shield
(GND)
i
Ammeter (high)
Ammeter
Common
(Floating)
Im
common
DC source
Ground noise
DUT is floating
X
No ground
loop noise
Figure 1. B2980A Series loating ammeter
