Objective
- Can assemble Summing Amplifier and Subtracting/Difference Amplifier circuits
- Can calculate gain based on input and output voltage and based on the theory of summing amplifiers and subtracting amplifiers.
- Can measure input and output impedance on summing and subtracting amplifiers
- Can create your own circuit
- Can measure the magnitude of the gain in the integrator and differentiator circuits at each frequency change.
- Can compare the magnitude of the cutoff frequency in integrator and differentiator circuits
- Can prove the influence of RC on the magnitude of the cut off frequency, band pass, output voltage and gain in integrator and differentiator circuits.
- Can mention the functions of integrator, differentiator and comparator circuits.
- Can compare two voltages from two different inputs on the op-amp
- Can prove integrator and differentiator circuits as filters and voltage comparators.
1. Basic Theory
With the advancement of technology, in today's market we can find a small package that can be called an op-amp or operational amplifier, where this type of electronic component has a wide range of uses, one of which is as an active filter.
An integrator circuit where if a digital signal or square wave is given to the input, the output will be in the form of a sawtooth, in its function as a filter, the integrator functions as an LPF (Low Pass Filter) / lower pass filter, namely a filter that functions to pass low frequencies.
2. Feedback
Feedback (+) and Feedback (-)
Feedback Function:
- improve the quality of the output signal
- improve frequency response
- increase the width of the field (band width)
- reduce noise
Types of Feedback:
Series Input Voltage Feedback
Z in increases Z out decreases
Parallel Input Voltage Feedback
Z in decreases Z out decreases
The types of filters above are very suitable for use as buffers in electronic circuits.
Series Input Current Feedback
Z in increases Z out increases
Parallel Input Current Feedback
Z in decreases Z out increases
3. SUMMING AMPLIFIER (Summing Amplifier)
It is an inverting amplifier with two or more inputs connected together (into one), the summing circuit can be either non-inverting or inverting. The inverting type is easier to plan and build than the non-inverting type. If the desired output is inverted, then an inverting voltage follower can be used after the summing amplifier.
The output voltage of the inverting summing amplifier will be inverted and equal to the algebraic sum of each time difference of the input voltage and each input resistor and feedback resistor, which can be expressed as:
Vo = -[(Rf/R1) V1 + (Rf/R2) V2 + ... (Rf/Rn) Vn]
= - Rf (V1/R1 + V2/R2 + ... Vn/Rn)Information:
n = number of inputs
If all external resistor values are the same, then for all installed resistors:
(RF = R1 = R2 = R3 = ... Rn)The output voltage will be obtained from the algebraic sum of the input voltages with the reversed sign, expressed as:
Vo = - (V1 + V2 + ... Vn)The current flowing through the feedback resistor (Rf) is the sum of the currents flowing through all input resistors. The summing amplifier must have a feedback resistor (Rf) that is larger than its input resistors.
The summation scale will be differentiated by the value of its input resistor, so that the input voltage will be amplified than the others.
4. DIFFERENCE AMPLIFIER (Different Amplifier)
Difference Amplifier or substacting Amplifier is a voltage comparator with closed loop mode, where the magnitude of the output voltage can be written using the formula:
Vo = - (Rf/R1) V1 + [(R3/(R2+R3)) ((R1+Rf)/R1)] V2
//bila R1=R3 dan Rf=R2 maka, menjadi:
Vo = -(V1-V2)
= V2-V1The first minus sign in the formula is an indicator that the output polarity is the same on the comparator. If the voltage on the inverting input is more positive than the voltage on the non-inverting input, the output voltage will be (-), the opposite will occur if the inverting voltage is smaller than the non-inverting voltage.
Differentiator / Differential Amplifier has the possibility to change, small voltage differences into larger voltage signals. With very low input impedance and this type of circuit can be isolated (buffered) with a voltage follower amplifier.
Integrator
Simple Passive Integrator
Vo = XC / R + XC * Vi
XC = 1 / (2 * phi * F * C)
Op-Amp as an Active Integrator
AV = Δt / RC
ΔVout = Vin * Δt / RCDifferentiator
Simple Passive Differentiator
Op Amp As Active Differentiator
AV = RC / Δt
Vout = - RC * ΔVin / Δt
Active Differentiator Improvisation
Op-Amp can also be used as a filter, integrator, differentiator, and comparator.