Basic Operational Amplifier Building Blocks
We have seen throughout this operational amplifier
section that we can connect resistors to a basic operational amplifier
to produce various inverting and non-inverting outputs and
configurations along with their respective gains. So to make things a
little bit easier for all, here is a list of some of the “Basic
Operational Amplifier Building Blocks” we can use to create different
electronic circuits and filters.
The Voltage Follower
The Voltage Follower, also called a buffer dose not amplify or invert the input signal but instead provides isolation between two circuits. The input impedance is very high while the output impedance is low avoiding any loading effects within the circuit. The gain of the buffer is +1 and Vout = Vin.The Voltage Follower Op-amp Circuit
The Op-amp Inverter
The Inverter, also called an inverting buffer is the opposite to that of the previous voltage follower. The inverter does not amplify if both resistances are equal but does invert the input signal. The input impedance is equal to R and the gain is -1 giving Vout = -Vin.The Op-amp Inverter Circuit
The Non-inverting Amplifier
The Non-inverting Amplifier does not invert the input signal or produce an inverting signal but instead amplifies it by the ratio of: (RA + RB)/RB or commonly 1+(RA/RB). The input signal is connected to the non-inverting (+) input.The Non-inverting Op-amp Circuit
The Inverting Amplifier
The Inverting Amplifier both inverts and amplifies the input signal by the ratio of -RA/RB. The gain of the amplifier is controlled by negative feedback using the feedback resistor RA and the input signal is fed to the inverting (-) input.The Inverting Op-amp Circuit
The Voltage Adder
The Adder, also called a summing amplifier, produces an inverted output voltage which is proportional to the sum of the input voltages V1 and V2. More inputs can be summed. If the input resistors are equal in value (R1 = R2 = R) then the summed output voltage is as given and the gain is +1. If the input resistors are unequal then the output voltage is a weighted sum and becomes:
Vout = -(V1(RA/R1) + V2(RA/R2) + etc.)
The Voltage Adder Op-amp Circuit
The Voltage Subtractor
The Subtractor also called a difference amplifier, uses both the inverting and non-inverting inputs to produce an output signal which is proportional to the difference between the two input voltages V1 and V2. More inputs can be subtracted. Resistances are equal (R = R and RA = RA) then the output voltage is as given and the gain is +1. If the input resistance are unequal the circuit becomes a differential amplifier.The Voltage Follower Op-amp Circuit
The Op-amp Comparator
The Comparator has many uses but the most common is to compare the input voltage to a reference voltage and switch the output if the input voltage is above the reference voltage. If the input goes more positive than the reference voltage set by the voltage divider, Vin > Vref, the output changes state. When the input voltage drops below the preset reference voltage and Vin < Vref, the output switches back. By using negative feedback the comparator can be converted into a Schmitt Trigger circuit.The Comparator Op-amp Circuit
