I'm having problems with using a summing amplifier. I don't know if it's the chip or needs a ground that is both positive and negative. I'm using a jfet input OP amp, I think it doesn't need to be a jfet input, but that is the chip I have. Please someone help me
The TL072 is basically a low noise HiFi audio amplifier and would not be the optimum choice for a summing amplifier, but it would be adequate, unless high precision is required. A much more suitable opamp would be from the OPA192 family of opamps.
https://www.ti.com/lit/ds/symlink/opa192.pdf or the related cheaper, but less accurate, OPA197 family.
https://www.ti.com/lit/ds/symlink/opa197.pdf
The input voltage range of the TL072 is -Vcc +4V to Vcc -4V (-Vcc can range from -5V to -15V, while Vcc can range from 5V to 15V).
Similarly, the TL072 output voltage does not swing from -Vcc to Vcc
Because of this, it is difficult to use the TL072 as a traditional, DC coupled, inverting virtual earth summing amplifier with a single supply line.
The simplest solution is to generate a second supply line using an inverting charge pump power converter. **broken link removed**
The TL072 does have the major advantage of FET inputs which means, for practical considerations, the inputs do not take any bias current, thus eliminating voltage errors caused by the input bias current flowing through the input and feedback resistors.
https://www.ti.com/lit/ds/symlink/tl074a.pdf
Some opamps, like the OPA192 family for example, have an input voltage range from -Vcc to Vcc and also an output voltage range from -Vcc to Vcc. This is known as Rail to Rail Input/Output (RRIO).
RRIO opamps can be used as inverting virtual earth summing amplifiers, with a single supply line, under the following conditions:
(1) -Vcc = 0V, Vcc = supply voltage. Input voltage = 0V to minus voltages
(2) -Vcc = supply voltage, Vcc= 0V. Input voltage = 0V to positive voltages
spec
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