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The Differential Mode Op-Amp. What is the Differential Mode ?. The op-amp can be connected up in various ways or modes . What it does depends on how it is connected up.
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What is the Differential Mode ? • The op-amp can be connected up in various ways or modes. • What it does depends on how it is connected up. • When connected up in the differential mode, it finds the difference between the two input voltages and multiplies it by the gain.
The Differential Mode Op-Amp The feedback resistor ( Rf ) is used to control the gain of the op-amp. The input voltages are fed in through the input resistors ( R1 andR2 ). Rf R1 +Vs - R2 + -Vs V1 Vo R3 V2 0 V R3 is always the same size as Rf.
Revision – The Gain of an Amplifier You may remember from Standard Grade that the gain of an amplifier is the ratio of the output and input voltages. The gain can also be expressed in terms of the resistors used to connect up the op-amp.
Example 1 Calculate the output voltage from the op-amp below. 150kΩ 20kΩ +Vs - 20kΩ + -Vs 0.3 V Vo 150kΩ 0.5V 0 V
Example 2 What size of feedback resistor would be required to produce an output voltage of – 6 volts ? Rf 20kΩ +Vs - 20kΩ + -Vs 0.6 V - 6 V R3 0.3V 0 V