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A DC offset question for mixer

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davison7

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Hi!everybody,

The double-balanced mixer (Gilbert mixer) is composed of three differential pairs that include the RF stage and LO stage. If the differential pairs don't keep in ideal balanced character due to the process variation, it will have severe offset problem.
The above situation led me to think about if the passive mixer also has DC offset problem? The passive mixer is often composed of four transistors that operate as the switches controlled by the RF and LO signal. Because the circuit is not constructed of the differential pairs, I doubt if it produces the DC offset?
So could everybody help me to solve this question, I will appreciate your reply.
 

Yes. LO causes DC offset in both cases.
 

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