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Summation of two signals

Japhet55

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Whats the best way to sum two voltages in design. I have two dc voltages, one from a low pass filter and another from an external control signal. Whats the best way to add these two voltagee before inputting them to a single pin?
 

thunderdantheman

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You'll need to use an op-amp configured as an adder... have a read of this it's an excelent resorce for op-amps and their various configurations.
 

thannara123

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Whats the best way to sum two voltages in design. I have two dc voltages, one from a low pass filter and another from an external control signal. Whats the best way to add these two voltagee before inputting them to a single pin?
Hi may i know the purpose of summation of those signals ?
 

Japhet55

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Hi may i know the purpose of summation of those signals ?

Hi, thank you for your response. I intend on using the summed voltage as an input to a VCO. The external voltage is passed through a Potentiometer to kind of act as a phase shifter or control the frequency on what the VCO will output
 

KlausST

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Hi,

Often used: just two resistors.
But it's no "perfect" summation. The (only) drawback is that you lose a bit of gain.

If there is an active filter ... there is a good chance that there is one node with almost perfect conditions to "add" the external signal.

For better assistance we need to see your schematic.

Klaus
 

danadakk

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MFB might be one possibility. Here example is Khz LPF

1609934160008.png


1609934203224.png


1609934723741.png



Regards, Dana.
 
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Japhet55

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Hi,

Often used: just two resistors.
But it's no "perfect" summation. The (only) drawback is that you lose a bit of gain.

If there is an active filter ... there is a good chance that there is one node with almost perfect conditions to "add" the external signal.

For better assistance we need to see your schematic.

Klaus

What component can i use to add the voltage from the potentiometer with the one from the Low pass filter?

 

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KlausST

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Hi,
What component can i use to add the voltage from the potentiometer with the one from the Low pass filter?
We gave some solutions. What's wrong with them?

Klaus
 

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