Agilent Technologies U1401B, User'S Manual And Service Manual

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108 U1401B User’s and Service Guide
5 Application Examples
Operational Amplifier Verification
The ideal amplifier is assumed to have the following
characteristics:
• Infinite gain
• Infinite input impedance
•
Infinite bandwidth (a bandwidth extending from zero to
infinity)
• Zero output impedance
• Zero voltage and current offset
There are two basic ways of applying feedback to a
differential operational amplifier. One is by configuring the
operational amplifier as an inverting current- to- voltage
converter, and the other by configuring the operational
amplifier as a non- inverting voltage- to- current converter.
Current-to-voltage converter
An ideal operational amplifier can act as a
current- to- voltage converter. In
Figure 5- 13 , the ideal
operational amplifier maintains its inverting input terminal
at earth potential and forces any input current to flow
through the feedback resistor. Thus I
in
= I
f
and V
o
= –I
f
x R
f
.
Notice that the circuit provides the basis for an ideal current
measurement; it introduces zero voltage drop into the
measurement circuit and the effective input impedance of
the circuit as measured directly at the inverting input
terminal is zero.
1 Turn the rotary switch to the / position.
2 Manually select the DC 50 V range for the voltage
measurement.
3
Connect the red and black probe leads to the positive and
negative input terminals respectively.