In the integral operation circuit, the size of the capacitor is changed to make the time constant larger, the rise is slower, and the drop is slower. It is good, but this is not an effect. The most important obvious effect is that the front side of the negative exponential function curve is used for a small period. Therefore, the triangle wave formed is better linear!
The reason why the integral operation circuit produces errorsIn actual use, errors are prone to occur. There are two reasons.
1 The integrated op amp is not ideal. Due to the input bias current of the op amp, the offset current, and the input offset voltage, it will gradually rise to form the output error voltage. In addition, if the passband is not wide, the response to the rapidly changing input signal will be slow, and hysteresis will occur. Therefore, a low drift integrated op amp or FET op amp should be selected.
2 integral capacitors also cause errors. Due to the leakage resistance of the capacitor, it will gradually decrease, and at the same time, due to the adsorption effect of the capacitor, an error will also be caused. Therefore, capacitors with large leakage resistance, such as thin film capacitors, polystyrene capacitors, etc., should be selected.
Derivation integral operation circuitDerivation of this integral operation circuit as shown below
Virtual short feature: Vp=Vn=0, virtual break characteristic: i1=ic,
I1=(Ui - Vn)/R,ic= C x dUc/dt=d(Vn - Uo)/dt
Ui/R ​​= -C x dUo/dt, ∫(Ui/R)=∫[ -C x dUo/dt], Uo=-1/RC x ∫Ui.dt.
The integral operation circuit requires the period of the input square waveThe requirement of the integration circuit for the period T of the input square wave is: RC""TR.
C is the product of the input resistance R and the feedback capacitance C in the integration circuit.
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