Greetings,
Ive playing with integrators and differentiators in LT-Spice.
I first went to my old electronics text book (Sedra and Smith) and placed an op-amp down with a capacitor in the feedback path and had my RC combination = 1.
(R = 100k and C= 10u / R = 10k and C = 100u)
I sent in a 1v peak-to-peak sin wave (quick and simple).
On paper I should get a 1v peak-to-peak cosine wave out
With the combination R = 100k and C = 10u:
Well, I get a sinusoidal wave out but in the micro-volt range. (+120uv to -240uv)
It was recommended to put a large resistor in the feedback path. The result had a sinusoidal wave but again in the 200ish micro-volt range peak-to-peak.
With the combination R = 10k and C = 10u and w/o the large R in feedback:
Well, I get a sinusoidal wave at essentially the positive rail centered around 13.98v a couple micro-volts peak-to-peak.
Inserting the large resistor in the feedback path. The result had a sinusoidal wave centered around 24.3mv but again in the 200ish micro-volt range peak-to-peak.
Next,
I tried simulating a differentiator. R = 10k and C = 10u.
Again, driving a sine wave in 1v peak-to-peak, I get a signal hammering rail-to-rail (looks like a square wave)
I found the recommendation for a practical differentiator to place a capacitor in the feedback path. After placing this capacitor in the feedback path it worked, I get a 1v peak-to-peak sinusoidal out. (I assume cosine.)
So I get a practical differentiator to work.
Any suggestions for the integrator?
Schematic is attached.
Thanks
Sparky
Ive playing with integrators and differentiators in LT-Spice.
I first went to my old electronics text book (Sedra and Smith) and placed an op-amp down with a capacitor in the feedback path and had my RC combination = 1.
(R = 100k and C= 10u / R = 10k and C = 100u)
I sent in a 1v peak-to-peak sin wave (quick and simple).
On paper I should get a 1v peak-to-peak cosine wave out
With the combination R = 100k and C = 10u:
Well, I get a sinusoidal wave out but in the micro-volt range. (+120uv to -240uv)
It was recommended to put a large resistor in the feedback path. The result had a sinusoidal wave but again in the 200ish micro-volt range peak-to-peak.
With the combination R = 10k and C = 10u and w/o the large R in feedback:
Well, I get a sinusoidal wave at essentially the positive rail centered around 13.98v a couple micro-volts peak-to-peak.
Inserting the large resistor in the feedback path. The result had a sinusoidal wave centered around 24.3mv but again in the 200ish micro-volt range peak-to-peak.
Next,
I tried simulating a differentiator. R = 10k and C = 10u.
Again, driving a sine wave in 1v peak-to-peak, I get a signal hammering rail-to-rail (looks like a square wave)
I found the recommendation for a practical differentiator to place a capacitor in the feedback path. After placing this capacitor in the feedback path it worked, I get a 1v peak-to-peak sinusoidal out. (I assume cosine.)
So I get a practical differentiator to work.
Any suggestions for the integrator?
Schematic is attached.
Thanks
Sparky
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