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Operational Amplifiers. ABE425Engineering. Agenda. Packaging OpAmp as a near-ideal Voltage Amplifier Non-inverting OpAmp Virtual ground derivation Inverting OpAmp Virtual ground derivation Differentiating OpAmp Integrating OpAmp Voltage follower (buffer).
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Operational Amplifiers ABE425Engineering
Agenda • Packaging • OpAmp as a near-ideal Voltage Amplifier • Non-inverting OpAmp • Virtual ground derivation • Inverting OpAmp • Virtual ground derivation • Differentiating OpAmp • Integrating OpAmp • Voltage follower (buffer)
f5_21 Typical OpAmp pin assignment (741)
f5_22 OpAmp as a near-ideal Voltage amplifier • Open loop amplification A very large • Input impedance very high • Output impedance very low • OpAmp has a Voltage source output
Non-inverting OpAmp : Virtual ‘ground’ principle Since no current is flowing into the OpAmp: What is the input resistance for the source ?
f5_30 Inverting OpAmp
f5_30 Inverting OpAmp: Virtual ground principle Since no current is flowing into the OpAmp: What is the input resistance for the source ?
Capacitor equation Charge across Capacitor (Coulomb) Capacitance value (Fahrad (German for bicycle)) Voltage across Capacitor (Volt) Current through Capacitor (Ampere)
f5_31 Integrating Inverting OpAmp : Virtual ground
f5_31 Differentiating Inverting OpAmp: Virtual ground
Unity gain OpAmp (Voltage follower, buffer) • This circuit has no amplification, but provides a very high impedance input and low impedance output • Use it after any sensor configuration to prevent loading errors • You will need a symmetric power supply