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i made an inverting amplifier circuit using CA3130, the supply just the positive voltage and GND for V- supply. the circuit is used for full wave rectifier because the signal is around 1 MHz and 500 mV and i don't find any good diode for that frequency. the problem is, i expected only the positive voltage signal is produced but then the negative signal was appeared too in oscilloscope, how is this even possible?
simulate this circuit – Schematic created using CircuitLab
Thank you
Your 100 ohm resistor values are way too low and the input signal goes directly through them and to the output. 5V/100 ohms= 50mA. The output current of a CA3130 with a 10V supply is only about 4mA which reduces the output swing to 3V peak. Try 10k or 20k for the resistor values.
I don't see any source of negative voltage other than the input signal. I suspect your op amp circuit isn't working at all, and you're seeing the input signal appear at the output. Connect a probe to the input and see if the output is getting inverted as expected.
Instead of discovering wheel again, how about using Ideal Diode configuration?
The voltage drop VF across the forward biased diode in the circuit of a passive rectifier is undesired. In this active version, the problem is solved by connecting the diode in the negative feedback loop. The op-amp compares the output voltage across the load with the input voltage and increases its own output voltage with the value of VF. As a result, the voltage drop VF is compensated and the circuit behaves very nearly as an ideal (super) diode with VF = 0 V.
Source: https://en.wikipedia.org/wiki/Operational_amplifier_applications#Precision_rectifier
This way you will stay in safe side in means of absolute maximum rating for input which is Vss-0.5v (Ref: https://www.intersil.com/content/dam/intersil/documents/ca31/ca3130-a.pdf)
Edit: I didn't state my reasoning clearly. As far as i understand, the problem arises when 0.5V input voltage spec is taken into account. It's hard to find low Vf and high speed diode but this changes when low Vf spec is relaxed; since 1N4148 alike components become possible to use.
So consider this an alternative solution.
