32.
INTEGRATION.
a. An integrating circuit is often referred to as a storage
circuit, since the output voltage is proportional to the total amount
of energy stored. Any lowpass RC or RL circuit which has a long
time constant as compared to the reference periods of the applied
waveform acts as an integrator. In a series RC circuit, the
integrated output is always taken across the capacitor; while in a
series RL circuit, it is always taken across the resistor.
b. The output voltage Ec of an RC integrator circuit is
proportional to the total charge of the capacitor. The greater the
charge, the greater the amount of energy stored and the higher the
output voltage across the capacitor. When a constant DC voltage is
applied to an integrating circuit (Figure 43B), the output voltage
increases at a constant rate. When a constantly increasing voltage
is applied to an integrator circuit (Figure 43C), the rate of
increase of the output voltage increases at a rate that is
proportional to the increase in applied voltage and the length of
time that the voltage is applied to the circuit. The resultant
voltage has a parabolic waveform. When a sine wave is applied to an
RC integrator circuit (Figure 43D), the output waveform varies
sinusoidally but lags the input voltage by 90 degrees.
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