SUMMING AMPLIFIER INTEGRATOR DIFFERENTIATOR COMPARATOR OP-AMP CIRCUITS SUMMING AMPLIFIER INTEGRATOR DIFFERENTIATOR COMPARATOR

SUMMING AMPLIFIER May be inverting or non-inverting More than one input Output is the amplified sum of the input signals

Inverting Summer Applying KCL at the inverting terminal node, V1 Vout RF Vout i1 i2 i3 i4 Applying KCL at the inverting terminal node,

Where, The output voltage is the sum of the three input voltages, with different weighting factors.

If the three input resistances are equal , i.e. R1 = R2 = R3 = R

Non-inverting Summer V2 V1 Vout R1 R2 RF RS V+ Applying superposition theorem, i.e. apply one input at a time and determine the corresponding output, then combine the results.

Output due to V1 only V1 R1 R2 RF RS V+ Vout1

Output due to V2 only Vout2 V2 R1 R2 RF RS V+

Combining the two individual results, For n inputs and with R1 = R2 = Rn = R,

Vout = - [0.5 sin(1000t) + 0.33 sin(3000t)] Example 1 Calculate the output voltage for the circuit below. The inputs are V1 = 50 mV sin(1000t) and V2 = 10 mV sin(3000t). V2 V1 Vout 10 k 33 k 330 k Answer Vout = - [0.5 sin(1000t) + 0.33 sin(3000t)]

Example 2 Find Vout using the superposition theorem. Answer 1 k 9 k 2 k 3 k Answer Vout = 6V1 + 4V2

Applications - DAC A binary-weighted resistor DAC +V RF 8R 20 4R 21 2R Vout +V 21 20 22 23

R/2R ladder DAC 2R R RF Vout D1 D0 D2 D3 inputs 2R

INTEGRATOR R C Vin Vout

Input & ouput waveform INPUT OUTPUT

A Practical Integrator A shunt resistor added in parallel with capacitor – to prevent saturation R C Vin Vout RF

DIFFERENTIATOR R C Vout Vin

Input & output waveform

A Practical Differentiator A shunt capacitor and a series resistor are added – to reduce high frequency noise RS C CF R Vin Vout