5
Application Examples
120
Keysight U1401B User’s and Service Guide
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
, 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.
4
Connect the red and black alligator leads to the positive and negative output
terminals respectively.
5
Connect the operational amplifier as shown in
6
Use a DC power supply with
+
15 V and –15 V outputs to power the operational
amplifier.
