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Summation of two signals

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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?
 

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.
 
Japhet55 said:
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?
Click to expand...
Hi may i know the purpose of summation of those signals ?
 

thannara123 said:
Hi may i know the purpose of summation of those signals ?
Click to expand...

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
 

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
 

MFB might be one possibility. Here example is Khz LPF

1609934160008.png


1609934203224.png


1609934723741.png



Regards, Dana.
 
Last edited:


KlausST said:
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
Click to expand...

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

 

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Hi,
Japhet55 said:
What component can i use to add the voltage from the potentiometer with the one from the Low pass filter?
Click to expand...
We gave some solutions. What's wrong with them?

Klaus
 

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