Hi all,
I need to design a circuit to answer an EE assignment question. The main requirement is to apply a positive or negative DC offset to a potentiometer-supplied voltage. The assignment has an op-amp theme.
Additional requirements:
* DC offset must cover pot's entire output swing i.e. 5V pot output can have a -5V DC offset applied.
* DC offset must be controllable from a buffered control voltage e.g. DAC (I'm assuming buffered is to prevent an easier solution such as this: https://norcim-rc.club/Radio3_files/image012.jpg)
* Minimal additional components
Interpreted schematic for question:
DC Offset control circuit:
My initial thoughts were to use two opamps - one configured as a summing amplifier and one as a differential amplifier, to control the positive and negative offsets. Implementation below.
Whilst this works, it has the following drawbacks:
* Requires two control voltages so doesn't meet requirements
* Seems overly complicated - gut feeling is this can be achieved with a single opamp.
I'm currently stuck on how to overcome these. I suspect the top stage can be removed by injecting the negative offset voltage between the bottom stage's R8 and ground, but I'm still left with two indepentant control voltages.
Any help would be much appreciated.
Kind regards,
David
I need to design a circuit to answer an EE assignment question. The main requirement is to apply a positive or negative DC offset to a potentiometer-supplied voltage. The assignment has an op-amp theme.
Additional requirements:
* DC offset must cover pot's entire output swing i.e. 5V pot output can have a -5V DC offset applied.
* DC offset must be controllable from a buffered control voltage e.g. DAC (I'm assuming buffered is to prevent an easier solution such as this: https://norcim-rc.club/Radio3_files/image012.jpg)
* Minimal additional components
Interpreted schematic for question:
DC Offset control circuit:
My initial thoughts were to use two opamps - one configured as a summing amplifier and one as a differential amplifier, to control the positive and negative offsets. Implementation below.
Whilst this works, it has the following drawbacks:
* Requires two control voltages so doesn't meet requirements
* Seems overly complicated - gut feeling is this can be achieved with a single opamp.
I'm currently stuck on how to overcome these. I suspect the top stage can be removed by injecting the negative offset voltage between the bottom stage's R8 and ground, but I'm still left with two indepentant control voltages.
Any help would be much appreciated.
Kind regards,
David
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